1990 - Fischer, J.L- Historia temprana de la embriología.pdf

8/13/2019 1990 - Fischer, J.L- Historia temprana de la embriologa.pdf

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Int. J .I)( ' \' . lliol. J ~ : 1 1- 2 .1 (19IJO) 11

Experimental Embryology in France(1887-1936)

I. T he fo un din g fa th ers o f e xp erimenta l embry olo gyF ro m th e p Oin t o f view o f th e b io lo gica l h isto ria n, e xpe rim en ta l

e mb ryo lo gy w as b orn in th e 1 88 0s th ro ug h th e la rg ely s im ulta ne ou swork of Hermann Fol and Stanislas W arinsky in Switzerland. ofW ilhelm R oux in G erm any and of Laurent C habry in France (O ppen-heimer.1967: Churchill. 1973: Fischer. 1986: Horder et a l. . 1 986) .Of t he th re e c ou ntr ie s. it w as G erm an y th at p ro du ced th e g rea te stnumber of e mb ryo lo gists spe cia lize d in th e n ew d iscip lin e. T his ca nbe easily understood when we consider that it was also in Ger-m anyft that em bryology gained scientific status in 1817. thanks toth e re se arc h o f C hristia n P an de r (B ala n. 1 97 9). fo llo we d b y that ofErnst Von Baer. Johannes Muller. Heinrich Rathke. etc.: that is.there w as in that country a tra ditio n o f e mb ryo lo gy a nd a p oliticalawareness of the need to support M basic researchft that causeddevelopm ental science. in its early experim ental phase, to be es-sentially G erm an. From W . R oux to H . Spem ann, w ho w as aw ardedthe N obel Prize in 1935. there are num erous nam es of distinctionin th is fie ld .

The French contribution was more m odest in lhe early days ofexperim ental em bryology. w hich has also been given the nam es ofd ev elo pm e nt al m e ch an ic s (Entwicklungsmechanik) (Roux, 1884:Churchill. 1975). biomechanics (Delage. 1895). developmentalp hy sio lo gy (C au ll er y.1 93 9) a nd c au sa l emb ry ol og y(B ra ch et.1 92 1).And this contribution, despite its m odest proportions. w as never-theless marked by research that contributed to furthering our

JE AN -LO UIS FIS CH ERC en tre A le xa nd re K oyre . H is to ;re d esS cie nc es e t d es T ec hn iq ue s, P aris . F ra nc e

kn ow le dg e o f e mb ryo lo gy. T hre e names illu stra te th is p erio d: L .Chabry. Y . D elage and E. Bataillon.

This study w ill be lim ited to the peflod betw een the years 1887and 1936 -1887 being the year that L. C habry defended the thesistha~ became the seminal text for e xpe rim en ta l em bryo lo gy inFrance.and 1936 being the date that corresponds to the thesis ofE. W olff. w ho w as. together w ith L. G allien. the founder of a schoolof em bryology that generally set the pattern for -developm entalbiologyft as w e know it in France today.T he m o ns tr ou s ascldlans

Laurent Chabry (1855-1893) had all the qualities necessary fora g re at c are er in s cie nc e ( po uc he t. 189 3: F ischer and S mith. 198 4:Fischer. 1990)_ And yet he was refused important teaching posi-tions because he had been an adherent of, and participant in. the re vo lu tio na ry colle ctivism m ove me nt o f J. G uesd e. w ho w as n otmuch in favor w ith the politicians of the time. This explains whyChabry had to abandon experimental science and the nationallaboratory system and turn instead to making dental protheses ina p riv at e o ff ic e.

The evolution of C habry's scientific w ork follow ed a perfectlylogical pattern. As a m edical student in Paris. he w as particularlyinterested in the courses on physiological and anim al m echanicstaught by E.J. Marey at the College de France, towards the end ofthe 1870s (J. M arey. 1868. 1872 and 1878. in F ischer. 1990 ). In

.A ddress for reprints: Centre A lexandre Koyre. H isto ire d es S cien ces e t de s T ech niq ues. 5 7 rue C uv ie r. F -7 52 31 P a r i s c ed ex 0 5. F ra nc eO.: 14.62R2190C L L l C P H1 ', ,, . .. 1 1 0 r~'


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12 .lL Fischer

Fig. 1. P ro fe ss or E ug en e B ata illo n (/864-1953)

1881, C habry defended h is me dic a l d is se rtat io n. entitled Contribu-tion a {'etude du mouvement des cotes et du sternum (Contributionto the Study of M ovem ent of the R ib C age and the S ternum ). Thisthesis w as a w ork steep ed in th e m etho do lo gy d e v e lo p e d b y Marey.Chab ry con ti nued his study of animal m echanics and authoredpape rs en ti tl ed Mecan ism e du sau t (T he m ec ha nic s o f ju mp in g)(1883), Sur Ie mecanisme de fa natation des poissons ,- (Themechanics o f swimm ing in f is h) (1883) an d Su r la lo ng ue ur de smembres des animaux sauteurs (The length of members injumpi ng a nima ls )( 1885 )

It w as the im pulse gIVen by the convinced p ositivist , G eorgesP ou ch et, d ire cto r o f th e la bo ra to ry o f m arin e z oo lo gy a t C on ca rn ea u(Pettit, 19 02 ) th at propelled C habry, an a ssociate director of thatla bo ra to ry , to wa rd s c ellu la r m ec ha nic s. T he o rig in ality o f C ha bry 's1887 thesis, E mb ryo fo gie n orm ale et teratologique d es A sc id ie s(N orm al and Teratolog ical E mbryolog y of A scidians) lies not o nl}' inhis scientific method. but also in his ability to manufacture thein stru me nts in dis pe ns ab le fo r c arry in g o ut n ew e xp erim en ts .

Here again w e m ay recall how C habry w as influenced by M arey,who wrote: The experimenter must know at every instant how tom odify the instrum ents that he uses and often how to m anufacturethem him self (18 78). C habry's thesis is concerned prim arily w iththe teratolog y of tunicates produce d by experim ental techniques,and only seconda rily w ith no rm al ascid ian em bryo logy.

C habry observed th e diffe rent stages of segm entation in Ascidiaaspersa using material regularly dragged up from the sea bed.Several successive catches provided specim ens w hose eggs alls ho we d a bn orm al s eg me nta tio n. S uc h m on stro us s eg me nta tio nh ad a lre ad y b ee n o bs erv ed (Quatrefages). B ut th e h is to ry o f b io lo gyabounds with such cases judged to be of ~no interest'. within aparticula r sociocultu ral context, even though they o ften do tu rn outto be of very considerable interest. Such was the case with thea bn orm al e gg s of Ascidia aspersa.

In fact. Chabry had no other suitable m aterial ready at hand andhe therefore studied these eggs while waiting for a fresh. norm albatch. H e noted the strict relationship existing betw een faulty orabnormal segmentation. cell death and the production of mon-strous larvae. In his own words. here was an absolutely newsubject~ . H e observed th at th e death (sphacele) of a blastom ere atstage II p rodu ced a half-em bryo . D eath at a rater stage (IV ) resu ltedin organic agene sis that w as specific for the particu lar b lastom ereaffected. Thus, lack of the left superior blastom ere at stage IV ledto larval forms from which the otoliths were missing. After thesefin din gs . C ha bry wro te : F ro m h ere it is e as y to re ac h th e c on clu sio n(which I believe to be valid only for Ascldians and anim als whoseblastom eres differentiate early) that each blastom ere containsc erta in p ote ntia l p arts w hic h. If d es tro ye d, a re irre me dia bly lo st a ndthat different parts of the animal are preformed in the differentre gio ns o f th e e gg (C ha bry . 1 88 7).

T his rem ark. the re sult of sim ple obse rvatio n. raise d im po rtantquestions which were debated not only at that tim e, but also m uchlater. These were the problems of mosaic eggs and of theirN pre fo rm is t c oro lla ry (a n otio n w hic h. in cid en ta lly , b ea rs n o re la -tio nship to th at of th e pre-existence of germ s. a s certain historiansc on tin ue t o b elie ve ) ( Ro ge r, 1 97 1; M aie nsc he in 1 98 6; R ey .1 98 9).T his p re fo rm is m. o r p re de te rm in atio n, w as to re ce iv e its m eth od ol-og y fro m W eism ann and m icrom erist theo ry.

S ubsequently. C ha bry thou ght he could, by m eans of a pinprick,produce a traum a harm ful enough to destroy a blastom ere and thusre pro du ce c erta in n atu ra l a bn orm alitie s th at h e c ou ld then s tu dy ind etail. A t t his point, C hab ry's technical skill cam e in to play. In orderto p erfo rm th es e e xp erim en ts , he conceived an apparatus w hichwas a m odification of the one he had built to observe norm al eggd ev elo pm en t in A sc id ia - a capilla ry specim en holder. Th is devicewas fitted w ith a fine glass needle drawn out over a flame. One ofthe tips of this needle was placed on a red-hot surface (platinumkn ife of a th erm ocautery) and then q uickly rem oved. T his o perationconcocted by Chabry produced a microcapillary. In this way, hein ve nte d th e m ic ro fo rg e a nd th e m ic ro ma nip ula to r. tw o in stru me ntso f great value to C habry (and to e mbryologists in gene ral), m akin git possible to destroy one or m ore blastom eres of a segm enting egga nd follow its developm ent after th e ope ration .

A cc ord in g to C ha bry , e xp erim en ta tio n w ou ld a lw ay s b e p os sib lep rovided the teratolo gical e ffect to be studie d - the result o f a chainof ca usally-related p henom ena - arose from a sim ple initial e vent.If s ev era l s uc h e ve nts w ere in vo lv ed . th en e xp erim en ta tio n w ou ld b ed iffic ult. F urth er, C ha bry re ma rk ed , e xp erim en ta l te ra to lo gy . s in ceit concerns norm al eggs, enables the chain of anatom ical events tobe studied. but tells us nothing of the initia l cause (1887). Herew as food for discussion, w ith its im plica tions of hereditary m alfor-m ations (i.e. mutations) contained in the eggs before division orexternal ag ression. w hose p rim e ca use re mains elusive. Th ere w asalso a w arning substance or a ph ysical act a s t he cause of an effect,


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for clearly the causes leading a normal and an abnormal egg toproduce a given monstrosity cannot be identical. The problem ofsubstances o r physical actions and their tera togen ic spe cificity onthe egg and the em bryo rem ained the subject of anim ated discus-sion in ca usal em bryo logy in the years tha t fo llo wed.

Be that as it may, Chabry was able to reproduce natural half-em bryos experim entally be destroying one of the blastom eres atstage II. Sim ilarly he produced embryos lacking otoliths. thusshow ing tha t the otolith w as lo calized in the low er rig ht blasto mereat stage IV. He discovered the regulatory ability of the left blasto-mere at stage II to give rise to pigment spot originating. as heshow ed exp erim entally, from the division of the right blasto mere(lo ca liz ed in th e lo we r rig ht b la sto me re a t s ta ge IV ). T he d es tru ctio nof 3 blastom eres at stage IV produced quarter-em bryos. etc.

T he se fa cts c on ta in ed s uffic ie nt m atte rto c on stru ct a p re fo rm is ttheor)' and defend au toge nic predeterm ination. H ow ever, C habrydid not venture along this path. He was reluctant to theorize andplun ged dee per into hi s experim ental or norm al observations ofascidian m onsters. How ever. he refused to generalize findings: The technique of cellular trauma should not always lead to thesam e results: although som e people m ay find decisive proof in m yexperim ents that the anim al is preform ed in the egg and that eachpart of the animal is preformed in part of the egg. I am anxious toavoid such a conclusion. which is far too absolute~ (1887).

S uch prudence proved to be justifie d, for alth ough E .G . C onklinconfirm ed C ha bry's experim ental re sults in 1905 (Conklin. 1905),A. Dalcq, in 1932-1938 showed by means of an experim entaltechnique (m erogony). invented by D elage. that the ascidian eggca n regulate ~ nder certain conditio ns (D alcq. 19 32, 1941). It isin fa ct a sp atial and tem poral relation that determ ines the isotropyor anisotropy of the egg. This is what leads the proponents ofp re fo rm atio n (n eo -p re fo rm atio n o r n eo -e vo lu tio n. te rm s e mp lo ye dby biologists at th e end of the 19th cen tury), like those propone ntsof a theo ry of epigenesis (neo -epigenesis), or eve n those w ho, m orera tio na lly . w is he dto re co nc ile th e tw o th eo rie s to s ee in th e a sc id ia negg e xam ples of alternatives to support their argum entation.Ep igenes is o r p re fo rma tion

In a ny c as e. in ta kin g u p th eo re tic al p os itio ns . s cie ntific fa cts a renot alw ays sufficient. C habry, w ho m ade the e xperim enta l dem on.stra ti on of neo-pre form ation, w as ag ainst g eneralizing this theoryb ec au se o f th e p olitic al id eo lo gy th at h e e sp ou se d. A cc ord in gto th isideology, m en are equal and free, and social constraints must becom batted. together with the inequality of classes: w hereas neo-preform ation is a th eory that im poses a biological co nstraint on theindividual. C habry w as exposing the shortco mings of a biolog icaltheory that ra n counter to his political and social theory; the refore.there could be no grounds for intellectual agreem ent between hisideology and scientific demonstration. On the other hand. A.W eism ann, who cam e from a Protestant fam ily that defended thefam ily line and the ~heredity~ of social class, was predisposed toe laborating a th eory of preform ation (H uard e t a l.. 1949) .

N eo -p re fo rm atio n a nd n eo -e pig en es is h eld a n im po rta nt p la ce inbiology debates at the turn of the century. W hile we cannot. with inthe scope of this article. present all the different positions givingrise to these debates, nor all the consequences they eventuallyhad. we cannot avoid m entioning the theoretical currents devel-o ping in France during th is period m arking the beg innings of causal

E .\p cr imc1 I1 al emh ry olo gy in F ra JI ce 1Jembryology.

In F rance , w ha t w e especia lly find is a neo-epig enetic ten dencyam ong the embryologists who expressed their choice of theory.From Y. Delage and E . Rabaud to P. W intrebert. scientists com batneo-preform ation on the grounds that they reject a ll system s thathold th at the ch ara cteristics of th e living being are predeterm inedin particles at the time of genesis - systems like that of A.W eism ann , w ith his ides~ an d idantes~. that of de Vries w ith his pangenes . or the chrom osom ic theory of heredity espoused byT.H. M organ. It was on the basis of som e deeply-held conviction,having more of sentim ent than of science, that em bryologists (orbio logists) becam e neo-epigenesists and n eo-L am arckian. sincethe one is generally accom panied by the other. and were opposedto n eo -p re fo rm atio nis m a nd n eo -D arw in is m. A nd If D ela ge p re fe rre dP. K ropotkine and his theory of entr'aide~ (mutua l assi stance) asa n e vo lu tio na ry fa cto r. ra th er th an D arw in ia n selection a nd M org a-nism .. and if the inverse tendency is m uch m ore pronounced in theEnglish-speaking countries, it is because both groups, thoughobse rving identical ph enom ena, each interpret the results in w aysth at s atis fy th eir w ay s of thinking and their w ish to explain the livingorganism with in different cultural fram eworks. Sea urchin or as-cidian em bryos do not change: when subjected to identical experi-m enta l pro cedures. they respond in sim ila r w ays: on ly the inte rpre-tations of the observers and experimenters change when con-fronted with the sam e b io logic al obj ec t. new s ien e

In 1887. Yves De la ge (1854-1920). one of the com mittee thate xam in ed Chabr y's thesis defended that year, was working onproblem s of physiology and particularly on the function of sem i-c ir cu la r c an a ls ~ a nd o to cy st s ~.I n 1 8 9 1, w h en B a ta illo n d e fe nd ed h is th e sis , D e la ge - presidentof Bataillon's exam ining com mittee - published an Essai sur lat he or ie d u re ve (E ss ay o n th e T he ory o f D re am s) (1 89 1). a fte r h av in gcarried out num erous studies on th e em bry olog y of sponges atRoscoff. He continued these studies w hile form ulating a num ber ofprecise theoretical ideas which first saw the light of day in 1895 inan ar ti cl e en ti tl ed , Unesci encenouve /l e: l ab iomecan ique - (1895),and which were developed in his work on heredity (1895). In th esam e year he la unched l Annee B io logique an d published a m an i-festo in favor of the change in orientation of bio logical rese arch inFrance in order to catch up with Anglo-Saxon work in the fields ofe m br yo lo gy a nd c ell p hy sio lo gy .

In D ela ge 's o pin io n, e mb ry olo gis ts (in clu din g h im se lf) h ad s pe nttheir tim e describing em bryos and com paring stages of develop-m en t. T his d es crip tiv e a nd c om pa ra tiv e e mb ry olo gy , c on ce rn ed w Iththe hows of ontogenesis, was in his view more or less wellunderstood . O n the other hand, the w hys rem ained obscure-(note that this why~ corresponds to the immediate cause ofphenom ena and not to the u ltim ate reason w hy ). For instance, w emay know everything about the form , the histology, the time ofappearance of the different types of cells during ontogenesis. butwe do not know why one cell becom es a neuron, another a musclecell and yet a noth er a glandular element. O f course it is necessa ryto posse ss a com plete description of phenom ena befo re b eing ableto provide an interpretation of them, and it is obviously easier tod es crib e th an to e xp la in . D ela ge . p erh ap s w ea ry o f h av in g d es crib edso m uch fine structure, decided to devote him self to explanation.


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14 .IL Fischer

Thinking of micromer is t theories, and certainly of W eism ann. hepointed ou t t ha t th e m os t p op ula r th eo rie s o f th e 1 89 05 w e re tho sethat emphasized the explanation of phenomena by a nuclearp re de te rm in ati on o f c ha ra ct er s. H ow ev er. D ela ge c on sid ered th atthis kind of theory was doom ed as a result, first. of experimentale vi de nc e p ro vin g the egg to be is otro pic (H . D rie sc h. P flu ge r. etc.)and . second. of the ph enom enon of regeneration. Thus , po si ti vedata proved that the egg does not contain predestined germ .

The egg is a cell w ith a determ ined physico-chemical constitu-t ion . Conf ident ly . D ela ge a ffir me d that the notion of hereditye xp la in ed n ot hi ng a nd th at, in ste ad , o ne s ho uld s ea rc h fo r d ire ctin gforces that w ill lead to histolo gical differentiation. S uch fa ctors a rethe t ro pi sms ~ a nd the tactlsm s ofW . P feffer (188 8) and W . R oux( 18 94 ). A pp ar en tly . D ela ge overlooked C ha bry (1 88 7), w ho te rm ed-attractio n- w hat D elage (1895 ) called cytotaxisH , R oux ~cytotro-p ;s m a nd H erb st ~ ch em ota xis - (s ee F is ch er et al..1984). AlthoughRoux was guilty of a sem antic error, the expressions used by theseauthors. a s w ell a s their m eth odolo gical im plica tions, w ere to takeon considerable importance in later years.

A cco rding to D elage, m esoderm al cells e nter into contact eithe rw ith endoderm or ectoderm by cytotaxis or chem otaxis rather thanas a result of the evolution of -gem mules that no one has everseen, or of som e hereditary m etaphysical tendency (D elage,1895).

If on top of this w e add the exogastrulation obtained by D riesch(1893) after placing sea-urchin eggs in water at 300 C, or theform ation of pse udoarthrose during fracture s, it w as no t surprisingto find functional excitation , formulated by Roux, evoked toexpla in these phenom ena; the ph ysiological exp lanatio n resides in-a uto mo rp ho sis - a nd -a uto re gu la tio n in w hic h o rg an s, tis su es o rcells develop in the direction in which they work and adaptc on tin ua lly t o t he ir f un ct io n .

The aim of this new science founded by Roux was the study of-p os itiv e fa cto rs o f o nto ge ne sis (s im ple m ec ha nic al. p hy sic al,chem ical or physiological effects), w hich w ould expla in develop-mental phenomena. It should be pointed out that the results ofC hab ry. D riesch, H erbst, R oux and O . H ertw ig had alrea dy se rved toopen the route along which Delage embarked in 1898 w ith thepublication of his note on Em bryos lacking a m aternal nucleus~.By m icrosurgery, Delage separated sea-urchin eggs into twoparts, only one of w hich possessed a nucleus. A fter fertilization ofeach fragm ent, D elage ob tained d ivisions. an d occasion ally larvaform s, from the part w ithout a nucleus (as little as 1/37th ofthe egg-1899). This experim ent was based on those of H ertw ig(1890) andB ove ri (18 89). The latter, using fore ign (hyb rid) sp erm , fertilizedportions of cytoplasm obtained by shaking virgin eggs in a glasstube, However, this method did not allow nucleated and non-nucleated fragments to be distinguished - as did the technique ofD ela ge (o r s o h e a ffirm ed ). In a ny e ve nt, th is m ero go ny (D ela ge 'sterm ) was in contradiction w ith the ~m erotom y experim ents ofB alb ia ni (1 89 2a ). -M ero to my c on sis te d in c uttin g a n in fu so ria nin to tw o h alv es : th e n uc le ate d p art re ge ne ra te d, w hile th e a nu cle atehalf degenerated. This type of experiment, repeated by otherw or ke rs (K le bs , 1887; Nussbaum. 1886; Verworn, 1891), led tothe affirm ation that the nucleus governs vital functions (Delage,1899a, b; Balb iani, 1892 a, b, c).

D ela ge 's e xp erim en ts o n m ero go ny H - p artic ula rly th os e (1899)that convinced him that Hm erogonial larvae possess a doublecomplem ent of chrom osom es (and not the sim ple set provided by

th e n uc le us o fth e s pe rm )-c om fo rte d h im in h is o rg an ic is t th eo ry .In th is way he was able to conclude that the nucleus of the ovule isnot req uired for fertilizatio n and, as a corollary, tha t fertilization isnot exclusively defined by the union of fem ale nucleus with a m alenucleus.

A n e xp erim en t d em on stra tin g th e u se le ss ne ss o f th e fe ma lenucle us w as a real go dsend for D elag e. In the ligh t of these re sults,he proposed a new, som ewhat ..animalculistic~ definition of fer-tiliz atio n w ith ou t e ntire ly re je ctin g th e a nc ie nt d efin itio n: T he u nio nof sperm atic nucleus and any given m ass of ovulary cytoplasm andthe transferto this ovulary cyto plasm of a special energetic pla sm ac on ta in ed i n the s pe rmo ce nt re ( De la ge , 1899b).

It w ould be inappropria te here to go into a detailed discussion ofthe validity of the expe rim en tal results. H ow ever, it is inte restin g toconsider the extrapolation m ade from them by other bio logists tosupport o r reject their hypotheses, It is w ell know n that b iologistshave alw ays been ready to twist their interpretation of facts in thew ay that best su its their personal view s of the living organism or theconcept they w ish to im pose.

Although D elage affirm ed the im portance of the cytoplasm , hedid not believe th at it ha d the m onopoly of directing pheno men a (asothers believed of the nucleus), but that the vital forces weregove rne d by the nu cleus an d cytoplasm together (protop lasm ).

A fter these exp erim ents, it w as only na tural that D elage sho uldturn his attentio n to parthenoge nesis. M erog ony is the u nion of tw osexual elem ents, whereas parthenogenesis concerns only thedevelopm ent of a larva from a m ature ovule (or the beginning ofa division of the egg - abortive parthenogenesis). The interestaroused by parthenogenesis at this tim e was prim arily due to thefa ct th at L oe b h ad ju st p ub lis he d (1899) h is f ir st r es ults c on ce rn in gp art he no ge ne tic s ea -u rc hin la rv ae , o bt ain ed b y c he m ic al t re atm e nto f u nf ert iliz ed e gg s.

It is unnecessary to go into the nu merous experim ental stu dieso n parthen ogenesis p erform ed b y D elage or the ecstatic gra titudeshowered upon him by a handful of fem inists for having at lastdelivered w om en from the sham eful bondage that obliges them toresort to m en in order to becom e m others (Delage et al., 19 13 ;Del ag e, 1 91 3) . M ore notew orthy is his theo ry of parthenogenesis(1 91 3), w ith its concep t o f Mco ll oida l morphogenesis (par thenoge-n etic agents w ere thought to b rin g a bo ut c oa gu la tio n a nd liq ue fa c-tion of elem ents con tained in th e pro toplasm H, thus triggering theontogenetic pathways). This theory was in opposition to that ofc h em ic al mo rp ho ge n es is _ of Loeb, but possessed sim ilarities toth e n otio n o f e le ctric m orp ho ge ne sis o f L illie . It w as fa r re mo ve dfrom B ata illon's theory of organic and h eteroplastic catalysis .

According to Delage, it was not worth paying attention top arth en og en etic a ge nts , fo rth e e ffe ctiv e c au se w as th e re ac tio nof the egg . This idea w as also to be developed by Bataillon. At theInternation al Z oolog y C ong ress in G raz (A ustria) (A ugust 15-20,1910), D elage read a long p aper on E xperim enta l P arthen ogene-sis in which he related the success of Bataillon in provokingtraum atic parthenogenesis in a vertebrate. He qualified this ex-p er ime nt a s ex tr ao rd in ar y ( De la g e, 1912).The golden age of biology

L ' ag ed 'o rd e f a b io lo gi e w as th e term u se d b y E ug en e B ata illo n(1864-1953) (Fig. 1), to qualify that period at the beginning of thec en tu ry th at m arked experim ental biology by the success o f e x -


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.--perimental parthenogenesis in a vertebrate. J. Loeb's successfule xp er iment s w it h p ar th en og en es is in sea urchins influenced allsubsequent r es ea rc h c ar rie d ou t on expe rimen ta l pa rt henogene si s.B oth D elage and B ataillon w ere greatly influenced by this type ofresearch.

B efo re b ec om in g i nt er es te d in e xp er iment al p ar th en og en es is ,Bataillon had studied the physiology and m etam orphosis of anu-r an s, w it h p artic ula r re fe re nc e to th e p hen om en a of histo lysis andrespiratio n w hich control th e a na tomic al m od ific atio ns of thetad p ole . C o nc lu d in g that the physiological determ inism of meta-m orphosis am ounts to little m ore than a c olle ctio n o f a sp hy xic

E \jh 'rim l'n ta l em hr y% , ,y in F ra nce 15

F ig . 2 . Professor Paul A ncel (1873-1961)

phenomena (1891), he also demonstrated the importance ofrespiration in the ontogenesis of fish and amphibians. In fact.Bataillon, by attributing to a physiological function - respiration - adeterm inin g role both in m etam orphosis and in the extensio n of th eblastoderm (1896), was perform ing chem ical em bryology beforeth is te rm e xis te d.

In 1894. A. Giard called the attention of physiologists to~an hydrobiosis , in oth er w ord s, laten t hfe. A s he w as in terested inthis problem , Bataillon was led by the results of a great number ofexpe rim en ts to generalize th e action of osm otic p ressure as a factorre sp on sib le fo r c erta in b io lo gic al e ve nts (1 90 1).


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16 JL Fisch,.,.A n elevation of osm otic pressure can, in certa in orga nism s. brin gsegmentation to a temporary halt in eggs that do not norm ally

display diapause. For a given concentration of NaCI, CaCI2 ors uc ro se , th e e ffe ct s are the same. Eggs tha t h av e b ee n in contactw ith salt w ater w ill. w he n pla ced in norm al w ater, g ive rise t o s im i la rabn orm alities of segm en tatio n, an d an excess o f o sm o tic p re ss ur ew ill produce double or m ultiple formations from lam prey eggs.B a ta il lo n c on fi rme d in vertebrates the results that L oeb (in 1892)h ad obta in ed by sim ilar m eans in sea-urchin eggs. In Bataillon'sview at this time. osmotic pressure was also respo nsib le for th eparthen og enetic dev elo pm en t of eggs.

In order to confirm the results o f L o e b in invertebra tes. as w ellas the experim ents of O . H ertw ig (1890 ). M organ (1899) a nd G ia rd(1900). B ataillon attem pted to obtain parthenogenesis in fish andam phibians and. in so doing . to discoverthe com mo n denom in atorg ov ern in g a ll th es e re su lts . H is e xp erim en ts p ro du ce d o nly a bo rtiv eparthenogenesis. Nevertheless. he w as able to dem onstrate thathis generalization concerning the effect of osm otic pressure w ascorrect. In this way. he refuted the notion of specific chem ical orionic effects. L ithium (M organ ). sa lt (H ertw ig) or su gar a re n o m orespecific as stimulators of ontogenesis than m agnesium (Loeb)(B ataillon . 1901 a. b . 19 04).

In this context. the work of Kulagin (1898) should not beforgotte n. H e obtained se gm entatio n in unfe rtilized frog e gg s th ath ad p re vio us ly b ee n tre ate d w ith a nti-d ip hth eria s eru m (B ata illo n.1900). Bataillon pointed out that the osmotic pressure of anti-diptheria (or normal) bovine serum is the same as that of 0.9%sodium chloride and carried out the following experiment: threeseries of unfertilized frog eggs fro m the sam e batch w ere tre ated forthree hours w ith a 1% solution ofN aCI. a 10% solution of cane sugaror bovine serum. Each lot. put back into running water, dividedirre gu la rly a fte r s ev era l h ou rs .

Not unnaturally. B ataillon underlined the role of osm otic pres-sure in this phenom enon. H owever. this notion could not explaineveryth ing: the ~ why of developm ent rem ained unansw ered. an dBataillon was obliged to turn to the neo-vitalism of the germanem bryologist. H . Driesch. with whose principles he was in totalagreement: It is a principle of correlation that dominates thee me rg en ce o f fo rm s ( Drie sc h, 1 89 9).

In other words, research into the mechanics of developm entshould be devoted entire ly to the more concrete ~how w i e ,w ithout . as Bataillon wrote, comprom ising itself in a vainresearch for the why (warum) .

Bataillon abandoned his studies on osmotic pressure, whichresulted only in abortive parthenogenesis and turned to hetero-geneous hybr id iza ti ons ~ (1910). In these experiments. he notedtha t c er ta in h y br id iz a ti on s (9 Bufo calami ta x d T ri tu ru s alpestris)r es ulte d in a b eg in nin g of d ev elo pm en t o f th e e gg s. In h is ~ sc ie ntifictestament' . he wrote concerning these findings the followingsentence. rem arkably instructive for w hoever wishes to grasp thelogic of his thoughts and to understand the scientific work that wasto follow: ' One Sunday in M arch 1910, I sat hypnotized in front ofm y m ic ro sc op e. c on te mp la tin g a n im pre ss iv e p ic tu re : a p re pa ra tio nof eggs of the toad Bu fo calam ita im pre gnated w ith spe rm from thenewt Tr itu rus a lpes tr is . The eggs were riddled w ith these strangem ale elem ents whose volum inous heads appeared on the slideslik e s o m a ny s urg eo n's s ty le ts ' ( Ba ta illo n, 1955).

It was at th is precise m om ent that the idea suddenly cam e to himthat a slight traum atism such as a prick from a sharp glass or m etal

needle could be as effective as heat or hypertonicity' . T his insig htwas no doubt partly the result of Chabry's teaching Bataillon histechniques during the years they spent together, which had givenhim an aptitude for tinkerin g about . A s soon as th e id ea had struckh im . B ata illo n a dm itte d th at ~ at o nc e~ h e p re pa re d ~ gla ss s ty le ts '.and put eggs from a ripe female on several watch glasses. Theresult was beyond all expectations: he obtained 90% abortivedevelopment. about 10% rudimentary embryos. but also a fewcases of swimm ing larvae. However. he believed that the latterderived from eggs that had been contam inated by sperm . Herep eate d his experim ents and. all doubts gone, p ublished his n oteon April 18. 1910. At last he had m anaged to obtain in vertebrateswhat Loeb had obtained ten years or so earlier in invertebrates.

How ever. the theoretical interpretation w as not sim ple. At theend of 1910. re-reading the latest volum e of Annee Bi%gique . hecame across a note b y G uy er: U nfe rtiliz ed fro g e gg s in je cte d w ithblood' (1907). Although parthenogenesis was not forem eost inGuyer's mind. Bataillon thought over the problem and saw in hisimagination the blood that had contaminated the eggs during hise arly e xp erim en ts o n tra um atic p arth en og en es is . W is hin g to re pe at(1911) on the frog the e xperim ents of Loeb in w hich unfertilized sea-urchin eggs were activated by low concentrations of cyanide,B ata illo n d is co ve re d th at h ig h c on ce ntra tio ns (0.5%-1%) of thischem ical dissolved the coat that covered the eggs. Quite fortui-tously. Batalllon now had in his possession a technique that was toenable him to carry out the crucial experim ent: eggs from whosecoat had been rem oved were divided into three lots. The first wasim pregnated with horse serum. the second with leucocytes, thethird with erythrocytes. each group of eggs being subjected to thetraumatic effect of the in jection. W ith the serum, no regularcleavage w as obtained: with the red blood cells about 1% regularc le av ag e w as o bta in ed : w ith le uc oc yte s. th e p ro po rtio n o f c le av ag eand gastrulae rose to 75% . 8ataillon com pleted these results byc yto lo gic al s tu die s a nd c on clu de d th at p arth en og en es is to ok p la cein tw o steps: activation by the pinprick an d reg ulation by in troduc-tio n o f th e n uc le us : it w as a n e xa ct re plic a o f n orm al fe rtiliz atio n (s eeb ib lio gr ap hy in F is ch er e t a l.. 1 98 4).

C ha bry. D elage a nd B ataillon can be consid ered a group. T hereare a great num ber of affinities in their theories apart from theirrejection of preform ation. They m ay be considered the first repre-se ntative s of this ne w bio logy w hose strong point is e xperim enta lembryology.

Although Chabry was not allowed to develop a school throughte ac hin g. in c om pe ns atio n D ela ge a nd B ata illo n d id b ec om e p ro fe s-sors who were able to form a generation of researchers. Delage.who taught at the Faculty of Science at the University of Paris.became in 1901 the director of the m arine laboratory of R oscoff.w hich he baptized as his 'B iolog ical S tation . The tea ching ca ree rof Bataillon was spent at the D ijon Faculty of Science, and also att ha t o f M o ntp ellie r.II. Emb ry olo gy a nd embryologists: from the College deFrance to a series of portraits

T his. then, is th e gro up of ' fo undin g fathers o f experim entalem bryolo gy in France. There are other group s th at w e could identifyon the basis of their sim ilar scientific interests o r the in stitution sthey belonged to. V . C oste. G . B albiani, F. H en neguy. and E . Fau re-Frem iet all held the Chair of E mbryology at the C ollege de France.


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Fig. 3. Jean R ostand (/894-1977) l oo ki ng a t P le ur od el es In L G all ie n'slaborarorv

P. B ouin. P. A ncel. R . C ourrier and E. W olff form ed another groupb elo ng in g to th e N ancy /S trasb ou rg scho ol of an ato my. h isto lo gyan d em bryo lo gy . T here w as also a g rou p o f peo ple b elo ng in g to theUniv er sity .c ompo se d o f n ames su ch a s A . G iard . M . C aullery . A .M ichel. E . R abau d. M . A belo os. P . W intreb ert, etc. A nd th ere w erethose w ho taught at the Schools of M edicine. such as L. Bard. M .A ro n, A . P renan t. etc. In ad dition to these gro up s. th ere w ere tho sewho w orked alone. such as J. Rostand or Dr. J. Balazuc. w hom wecite here from memory. since his thesis. La teratologie desco leo pteres et exp eriences de tran sp la ntatio n chez T eneb rio m oli-t or ( L.) dates back to 1948. This remarkable work. in the line ofentom ological teratology and em bryology of P. C appe de B aillon(19 27 ). w as n ever fo llow ed up . A nd w e cou ld co mp lete th e list w iththe histologists. the specialists in m arine invertebrates. for inadd itio n to th e ex perim entalists, th ere w ere th ose w hose w ork w asd es crip tiv e a nd who p ro ce ed ed from sim ple o bs erv atio n w ith ou t a ny

Experim el/lal cm /Jryology ill Frallc' 17

ex perim entation . T he w ork of th is ty pe o f research er is n ot w itho utinterest for the experim entalists, since it provides the basis foranalyzing the results of experim ents. A thorough know ledge ofnorm al developm ent is essential to understanding the m echa-nism s that experim entation brings to light. T he historian w hoattem pts to analyze experim ental em bryology from 1887 to 1936w ill find that the field is vast. and indeed far too vast to be able tod iscuss w ith in th e sco pe o f t his article all th e facto rs th at co ntrib u-ted to the developm ent of em bryology in France.T he C ha ir of Embryology at the College de France

O n A u gu st 4,1844, a ro yal de cree w as issued creatin g the C hairof Comparative Em bryogeny at the College de France for VictorCoste (1807-1873) (Faure-Fremiet, 1929a), w ho was nam ed for theChair on September 2. 1844. It is to Coste that we owe theintrodu ction into France of scientific e mbryology: he is th e on e w hom ade the break with a bs tra ct. sp ec ula tiv e emb ry olo gy d ev elo pe dw ithin the fram ew ork of tra ns ce nd en ta l a na tomy - c lo se ly re la te d tot he G er ma n Naturphilosophieor philosophy of n ature -of th e schoolo f E .R .A . S erre s a nd E . G eo ffro y S ain t-H ila ire .G e r a r d B alb ia ni (1 82 3- 18 99 ) (H en ne gu y, 1900) b ec am e C os te 'ssuccessor in 1874. after having been the head of histologicalre se arc h~ a t th e p hy sio lo gy la bo ra to ry o f th e Mus eum o f C . B e rn a rd .To him w e are especially indebted for his research entitled Onsexual p he no me na in in fu so ria ns ~ (1861) and ~ Research on g ermc on stitu tio n in th e a nim al e gg . b efo re fe rtiliz atio n~ (1 86 4). F orth iswork he w as twice awarded the M ont yon P hysiology Prize. w hich atthat time was a very distinguished award in the world o f s ci ence(Egli , 1970) . His Lessons on the generation o f ve rtebrates (1879)were edited by his pupil. F . Henneguy and becam e a fundament alwork fo r emb ry olo gists o f that period. The n am e of B albiani i s a ls oa ss oc ia te d w it h e xp er iments in m ero tom y and w ith A rc hiv es d A na -tamie mic roscap ique. w hich he founded together w ith L. R anvier in1897.In 1900, F. Henneguy (1850-1928) (Faure-Fremlet. 1929b),succeeded to the Chair of his professor. B albiani. like Balbiani. heha d spent a period of tim e at the laboratory of the Museum of C.Bernard. and had developed a passion for cytology, which wasbecom ing the leading discipline in biology thanks to the work of E.S trasb urg er (1 87 5) an d W . F lem ming (18 79 -18 82 ) o n cell division.If em bryo logists know of H en neguy esp ecially for his stud ies on theembryogeny of the trout (1889). he is above all. like Balbiani. acytologist and protozoologist: indeed. he recalled in 1901, M .Balbiani and I were the first. in France. to study karyokinesis (i.e.m it os is ) in a nim a ls ... ~.

Embryologists in the early 1880s were concerned with thestructure and functioning of the cell. This interest should beconsidered a logical outcom e of the studies of comparative em -b ryology that took the egg as their starting p oint. T he em bryolo gistscrutinizes the constitution of the ce ll (its protop lasm . its nucleus)a s the original elem ent of the organism a nd a s pa rt of a p luricellularwhole. but also as a specific unit. as a living being that nourishesitse lf and is reproduced (unicellular o rga nism s). Th is new gen era-tion of em bryologists of the 1880s also represents a break with thecom parative biologists of the period from 1860-1870. w ho, accus-tom ed to ~the Darw inian effect~, used em bryology with the aim ofd is co ve rin g th e p hy lo ge ne tic o rig in s o f liv in g b ein gs . N ow , p hy lo ge -netic problem s would no longer be the final aim of em bryological

--


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IX ./L . F is ch er

s tu die s. T hu s. H enne guy a gre ed w ith A . K ollik er (1 88 2), w ho w ro te : The right thing for embryology to do is follow its own path and.le a vin g a sid e phylogenetic hypotheses. work to discover the lawsgoverning t he format ion of organs (K6l1 iker. 1882).

H enneguy, w ho w as a contem pora ry of ~ biom echanicsff, w as byn o m ea ns a n in co nd itio na l b elie ve r in e xp er im e nt atio n. f or w ith ou tdenying th e im po rta nt role that it played in contributing to thepro gress of em bryolog ical kn ow ledge, he w as also convinced o f th eim portance o f th e role played by m ere observation. A fter a num berof years. he rem arked. em bryogeny has entered upon the expe-rim en ta l p ath wa y, a nd c erta in biologists w ho are attracted by thenew methods seem only to attach im po rta nc e to re su lts o bta in edby experimentation, and to consider simple observation as impo-tent for solving most problem s in embryology. W ithout sharing ttlisview, I consider that experimentation can yield great services toem bryogenists as a m ethod of controL .. ~ (Henneguy, 1901).

A s a c yto lo gis t, H en ne gu y re je cte d th e ~mic rome rist.. th eo ry o fWeismann. L ik e D e la ge a nd th e F re nc h mov em en t t ha t r eje cted th eneo-preformation theory, he remained convinced of the firm basisof the law s of hybridity: to be against the micromerist the ories ofheredity and against M organic genetics did not m ean a rejection ofMendelism.

H av in g le ft n um ero us e mb ry olo gic al w ork s o n s ex ua l c ells and onorganogenesis, H enneguy also distinguished him self with his re-search on protozoologyand on histology, d is cip li ne s t ha t c on tr ib u-ted to his em bryological research.Recallingtheteachings of H enneguy at the C ollege d e F ran ce, h isfo rm er pupil and son -in-law E . F aure-F rem iet w rote: -It is by delvingdeeply into his teachings, in which both the scientific and m oralseem to interlock, that one com prehends how important theinfluence w as of this p rofessor on those w ho had the oppo rtunit~ ' ofa pp ro ac hin g h im ( Fa un Hre mie t, 1 92 8).

Faure-Fremiet's view of himself was as follows: '.Born into afam ily of artists. where m y parents were my first teachers, it w asp er ha ps th ro ugh learning to see the form of beings and of objects,a nd t hr ou gh und er st an din g the m oving unity of a m elodic pattern,that I w as led towards the study of the living being (Faure-frem iet,1928). E m ma nu el F au re -F re m ie t (1883-1971) (Wil lmer, 1972).whose intellectual sensitivity had led him to see the logic of acontinuity between art and science, was designated the nextsuccessor to the Chair of Com parative E mbryogeny at the Collegede France, so dear to the scientific interests of Henneguy. He alsobegan work at the em bryogeny laboratory of the College de Francein 9 at first as a lab assistant, and late r as sub-director and asassistant professor, before being nam ed to the Chair in 1928.Fo r Faure-Fremiet. e mb ry olo gy is s im ply a c ha pte r in th e d ev elo p-mental sciences, which m ust resort to various biological disci-p lin es . R es ea rc h in e mb ry olo gy m us t b e s im ulta ne ou sly d es crip tiv eand m orphological, experim ental and physio logical. The idea ofdevelopment is in his m ind inseparable from the idea of theorganism or the living being (F aure -Frem iet, 192 5). H e further fe ltthat his stu dies (T he K in etic s o f D ev elo pm en t. C ell Multip lic atio na nd G rowth (1925) on p rotozoans and o n sexual cells, w hich w ereparticu lary useful models for understanding the mechanics ofdevelopm ent, w ere the resu lt o f this inte lle ctual achievem ent, an dgave a new m eaning to em bryology.

B alb iani, H ennegu y and Faure-F rem iet represent th e line of em -bf)'ologists that a pp ro ac he d d ev e lo pme ntal science throug h cy-to lo gy a nd p ro to zo olo gy . T he ~ pr oto zo olo gic al t en de nc y is th e o ne

that, in France, led to the establishm ent of genetics as a sciencein the 1940's, and it is therefore logical that B. Ephrussi learnedfrom Fa ure-Frem iet and pu blished together w ith him from 1925 to1928 (W illm er, 1972: 8urian e J a /. . 1 98 8).

As Faure Frem iet's successor in 1955, E. W olff broke with thet ra dit io n o f c yto lo gis ts a nd p ro to zo olo gis ts by in tro du cin g in to th eCollege de France a new tradition - that of the N ancy/Strasbourgschool of m orphology and em bryolo gy. T he C hair of C om parativeEmbryogeny was also to change names and become the Chair ofE xp erim en ta l E mb ry olo gy (1 95 5) (W olff, 1 95 5).The Strasbourg school of embryology: P. Bouin, P. Anceland E. Wolff

Because of the Prussian occupation, on M arch 19, 1872 th eMedical School of Strasbourg was moved to Nancy, which hadm anaged to avoid the occupation (M aubeuge, 1973). This was thedate that the Nancy School of M orphology was founded (Legait.1975). w ith Charles Morel and his pupil. Mathias Duval. withEdmond Lallement whose successor to the Chair of Anatomy,Adolphe Nicolas, who founded the Association of Anatom ists(1899), was to have Paul Ancel (1873-1961) as a pupil. Ancel(Wolff, 1962) would hold the Chair from 1907 to 1919. Morel'sC ha ir o f H is to lo gy w as eventually held by Leon Baraban and thenA u gu ste P re na n t, a utho ro ft he voluminous Elements d 'embryologiede I'hom me et des vertebres (1891). Later on, Pol Bouin (1897)worked under Prenant, who directed his thesis, and Bouin laterbecam e P renant's successor, in 1908.

After he had begun his curriculum in Nancy, Robert Courrier(1895-1986) (Jost, 1986), following the liberation of Alsace. wento n to S tra sb ou rg , w ho se U niv ersity revived and built a ne w M edicalS ch oo l. B ou in le ft N an cy a nd fo un de d in S tra sb ou rg the Inst itu te ofHistology (1919), and was later follow ed in the A lsacian capital byM ax Aron and Jacques B enoit. It was at this Institute that Courrierpursued his studies under B ovin and began his scientific career insexua l endocr ino logy.

S im ilarly, Ancel left Nancy to teach embryology at the newM ed ic al S ch oo l a t S tra sb ou rg (C ha ir o f E mb ry olo gy , N ov em be r 22 ,1919). A mong his earlie st collabo rators w ere P . V inte mbe rger. S .Lallem and (his daughter) and, a bit later, E. W olff.

In N an cy , B ou in a nd A nc el c olla bo ra te d together on research Insexual histophysiology, which was to lead them to the eventualdiscovery that the interstitial tissue of the testicle corresponded tothe only testicular endocrine gland secreting the male hormone:their work form s the basis of sexual endocrinology. In th is regard,an unsigned t ypescr ip t dat ed January 17,1940 has be en preservedi n t he dossier/file on P. B ouin in the archives of the Paris A cadem yof S ciences, sho wing that P . B ouin and P . A ncel w ere nominated fo rthe N obel P rize.

W hereas B ouin w as engaged in ca rrying out research in se xualh is to lo gy , h is to ph ys io lo gy a nd e nd oc rin olo gy in S tra sb ou rg , A nc el(Fig. 2) for his part was on the point of developing new lines ofresea rch in experim ental em bryolo gy, especially from 1924 on .Ancel was not the first to introduce experim ental em bf)'ology inFrance, but he was the one who gave it a new direction.

1924 w as the yea r of his first publications, in collabo ration w ithP. V intem berger, concerning the action of X rays on embryonicdevelo pm en t. A lth ough this w as n ot the first tim e that A n ce l w o rk e dwi th radio-b io logy - since he had, in 1907, p ub lis he d to ge th er w ith


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F ig . 4 . P ro fesso r M au rice C au llery (1 86 8-1 95 8). In t he ma ri ne la b or ato ryof W m1ere ux (destroyed d unng W orld W ar I/) in 193 8

Bouin a work on Rayons X et g landes gen it al es (X Rays and theGonads) - it was the first time that he had used this technique inem bryology: a ccord ing to E . W olff, it w as w ith P . V intem berg er thathe established the principal law s concerning the effect of X rays onthe cell. H e settled the question of the erstw hite stim ulative actionof these rays by show ing. on am phib ian egg s and bird bla stode rm s,that cells undergoing m itosis are not more sensitive than inter-phasic cells, but that the latter manifest their lesions during thecourse of m itosis Another very general law concerns the cumu-la tiv e e ff ec t o f d os es o ve rth e c ou rs e o f s uc ce ss iv e ir ra dia tio ns . H efurther show ed that em bryonic cells are radiosensitive during them orp ho ge ne tic p ha se s: a ll d iffe re ntia tio n p ro ce ss es c ea se in th es ecells. whereas cells that have not yet begun m orphogenesis at them om ent of irra diation can. in the future, carry out their differentia-tion (1 924. 1925, 1928). In add ition. A ncel an d S . Lallen.land w erea ble t o d oc um e nt t he p he no m en a o f ra dio ph yla xis in g er min at in gp la nt s ( 19 28 ).

In 1932, A ncel an d V intem berger bega n carrying out research onth e b ila te ra l s ym m etry o f th e fe rtiliz ed b ro wn fro g e gg - re se arc h th atw as still b eing co nducted in 193 8. C once rning this w ork. J. R ostand(1966) stressed that this bilateral symm etry corresponded to a

EXfll rim l lllall mhryology in France 19

fundam ental event in developm ent: the egg had atop and a bottoma nd m us t now have a rig ht and a left... M eanw hile, A ncel w elcom edE. W olff as his assistant in the laboratory. and proposed that W olff try to induce localized lesions on the chick em bryo . W olff beganh is re se arc h in F eb ru ary 1932, and then perfected. together withA nc el (A nc el a nd W olff. 1933, 1934). the technique of localized Xray irradiation on a territory of precise size and shape on a blasto-derm . Their aim was to identify and describe the precise organ-forming areas of the chick embryo. following the model that Vogthad established for the am phibian em bryo , Their results w ere notlong in com ing. and in 1933 W olff s ta rte d p ub lis hin g a s erie s o fte nnotes on om phalocephalic chick em bryos. on the topography ofp re su mp tiv e liv er p rim ord ia , o n th e e xp erim en ta l c re atio n o f d ou ble -hearted m onsters, etc. and a report entitled Recherches sur fastru ctu re d 'Omph alo ce ph ale s o bte nu s e xp er im en ta feme nt (Stu-dies on S tructures of E xperim entally O btained O mphalocepha licC hickens). In 1936 . he defe nded his thesis en titled, Les bases dela teratogenese experimentale des Veftebres amniotes, d 'apres lesresultats de m ethodes directes (The bases of experim ental terato-genesis in am niote vertebrates, as shown in results obtained fromdirect m ethods). M oreover, it was also in 1936 that W olff openedup in France a line of rese arch on se xual d ifferentiatio n, as a resultof the d iscoverie s m ade in sexual end ocrinolo gy a nd the success ofchemists, bioch em ists and th e che mical industry in extracting a ndm aking pure preparations from synthetic sex hormones (steroidhormones. 1935-1936) (Girard. 1933: Butenandt. 1936: Collin.19 38 : W olff. 19 46 ). T hus. in 1936. Wolff began e sta blish in g th ebases o f his future school.Por tr ait s o f embryo logi sts

Y . Delage had a considerable influence on m e: he was enthu-siastic and preached b y exam ple. MW ith this statem ent. written in1922, P . W in tre be rt a ck no wle dg ed his intellectual filiation a ndaffinity with the ideas of the French n eo -L ama rc kia ns in c re ati ng L ama rc ki an c hem is tr y , f rom w hich he d evelop ed his theory of theheredity of acquired characteristics. Paul W intrebert (1867-1966)(Grasse.1966), wh o began h is s cie nt if ic c ar ee r in m e dic in e,quickly turned to the biolog ical sciences. and studie d und er A lfredG ia rd . to w ho m h e o we d h is tra in in g. W in tre be rt s uc ce ed ed G eo rg esPruvot to the C hair of Com parative A natom y and P hysiology at thePari s Facu lty o f Sc ience in 1923 ( on J un e 9, 1923, this C hair w asto b e re baptized th e C hair of C om parative A nato my and H istology).U nder P ruvot. w ho ha d been the su ccessor o f L acaze-D uthie rs at th em arine science s labo ratory in B an yuls, W intrebert cultivated a life-long a ttachm ent to this im po rtant m arine b iology fa cility.

W e owe to W intrebert the discovery, in April 1906, of thepresence of Oiscogfossus pictus (O th.) in Banyuls. This anurana mp hib ia n w as to b ec om e a fa vo rite m ate ria l a mo ng e mb ry olo gis ts .H owever, it w as not until the years between 1928 an d 1931 thatW intreb ert carried out his extensive research on the e mbryology o ft he p ain te d frog. O ne year prior to the w ork of A nce l and V intem ber-ger, W intrebert had used the technique of staining to study thepatterns of bilatera l symmetry in the egg of Oiscoglossus. Th etechnique initiated by W . Vogt in 1925. which he perfected at th esa me tim e a s W eissenbe rg by using B ism arck brow n. also e nable dhim to define the fate maps of Oiscoglossus. But Wint rebert 'sconclusions have not survived. nor has the majority of his em-b ry olo gic al re se arc h. A s ta un ch b elie ve r in e pig en es is . w hic h fo r h im


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~o JL Fisch< '/

w as ~the only real m ode of development '. . h e a da pte d h is o bs erv a-tions to h is th eoretical id eolog y. C on trary to the ten den cy am ongmany embryo log is ts . who reached a com promise between pre-fo rm atio n a nd e pig en es is , W in tre be rt refused to go along with thisth eo re tic d ua lism : Epigenesis reveals. in am phibians, the exist-e nce of an in itiater center and a n o rgan izer center, w hich are, in thelitera l sense, g erm in al lo cations. b ut w hich differ essentia lly fromthose of the preformists in that they they do not contain organ-forming substances and are not predestined. They fulfill theinductor fu nc tio ns in th e em bryo. The latter m ust n ot b e c on fu se dwith the ulterior capacity of the cells of these centers and of theirfields of induction to differentiate the primordia induced by theorgan ize r cente r (1933).

Because his early training was in the field of comparativea nato my, W in trebert w as to rem ain through out his scientific careerdrawn more towards the study of function than to the study ofs tru ctu re (fa fo nc tio n f ait o rg an e) : R ln de ed , it is o nly b y a na ly zin gthe most intimate processes of functions. rather than by doingvio lence to living beings or imagining how they might be pre-organized, that w e will discover the secrets of life and evolution(1962).

At the age of 95 to 98. W rntrebert published a trilogy in which heexplains and develops his position on life and the living b eing: 1 ) Lev iv an t c re ate ur d e s on e vo lu tio n (The living being is the creator ofh is own evolution) (1962); 2) Le developpem ent du vivant par luimeme (The self-development of the living being) (1963): and 3)L exis tence del iv ree de I e xis tent ia lisme (E xis te nc e d eliv er ed fr ome xis te ntia lis m) (1 96 5). A mo ng a ll h is c on te mp ora ry s cie ntis ts , o nlyP .P . G rasse, due to a certain affinity of th eo re tic al id ea s, m a nife s-ted any interest in the work of W intrebert (G rasse, 1973).

W intrebert and Rabaud, who studied under Camille Dareste(Fischer, 1987a. 1989) and to whom w e owe the first experim entalproduction of monsters and the discovery of the duality of thecardiac primordium in the chick embryo, are today considered ofonly m argina l interest be cause their id eas are not recognized by th escientific community. From the point of view of the biologicalhistorian, these men held im portant institutional positions andattained these positions thanks to decisions m ade by their peers:they went along with a certain mode of thinking. and thereforebelonged to a scientific tren d that aton e tim e ha d possib ilities. Th eywere part of the scientific scene~ of a given period, and in thissense are w orthy of our attention. The Io giq ue d u vivant was notthe sam e for everyone.

How m any people are familiar today with the nam e of L. Bard?And yet this associate professor of the Lyon M edical School. whowas a specialist in tumors, discussed in 1886 on ~CeJlspec if ic ityand histogenesis in the em bryo~: he proposed the theory of thearbre histogenique, w hich view s all the cell lines involved in m akingup the future being as already predeterm ined in the egg cell. Thecells are not differentiated at the beginning of em bryogenesis butare, how ever, rigoro usly determ ined. C ell division is no thing m orethan the process of distributing the different categories of cell. Inthis theory, the anisotropy of the egg is absolute. W e owe to Bardthe clear developm ent of the thesis of cell lines using a genealo-g ic al tre e o f o nto ge ne sis (B ard , 1 88 6) th re e y ea rs b efo re D e V rie s(1889), to w hom this conce pt is generally attributed. B ard 's theoryis close to the m icrom erist theories of De V ries and W eism ann, andth ere fo re to n eo -p re fo rm atio n. B ard 's id ea lo gic ally c ou ld n ot a vo idtriggering the criticism of D elage, because it did not correspond to

the scientific ideals of the French bio logists of the period.For his part, A. M ichel, in the opening lesson of his course on

General and experim ental m orphology taught at the Sorbonne in1902, cam e out in favour of epigenesis and preached the ideal ofa m e ch an is tic f ut ure ( Mic he l. 1 90 2) .

In describ ing his re-encounter withJean R os ta nd (F ig . 3 ), B at ail-Io n re ca lle d th eir firs t c on ve rs atio n: T he re w e w ere a t th e b eg in nin gof the century, in that golden age of bio logy with its long list offam ous researchers: M organ and his fam ous team , those greate xp erim en te rs w ho se n am es a re L oe b, D ela ge a nd B ra ch et; W ils on ,S pem ann and that im pressive corte ge o f em bryologists that shedlight on the m echanics of early developm ent. From the am phibianto the sea urchin, from Drosophila to m an, from heredity and sex tothe transform ist hypothesis, our thoughts touched on all the greate n ig mas o f L if e ( Ba ta il lo n, 1953).

Jean Rostand (1894.1977) (Dubois. 1977; Tetry.1983: Fischer.19 87b) shares certain sim ilarities w ith D elage and B ataillon. W ithD elag e, becaus e h e w as attracte d from youth to the great problem so f b iology, a nd as the inventorof m erogony is responsible fo r havingawakened the French scientific comm unity to the im portance ofd evelop ing th e study of th is new biolo gy. W ith B ataillon, b ecause heundertook research that completed that of the discoverer oft raumati c parthenogenesis.

Sim ilar to Delage in his desire to m ake biology accessible to thelaym an, Rostand published, during the period we are concernedwith here, a num ber of works on biology designed for the generalread er, am ong w hich his L es c hro mo so me s, a rtis an s d e I h ert? diteet du sexe {C hrom os om es: th e artisans of he red ity and sex) (1928)w as espe cially single d out for sp ecial praise by B ataillon.

Duringthe 1920s, R ostan d p ublished m any notes on b iology andem bryology concerning insects, such as the habitat of pedogeniclarva of the M iastor genus (1922), half fly larvae obtained by eggligature (1927). The latter experiments were modeled on Spe-m ann's work on egg ligature in urodeles and the regulation of theegg.

The fascinating experim ent of Batail on, as R ostand called it.revea led tw o steps in the m echan ism of traum atic partheno gene-s is : a ctiv atio n a nd re gu la tio n. B ata illo n w as e sp ec ia lly in te re ste d inthe pro blem of a ctivation, w hereas R ostan d w orked on the pro blemof regulation. It was through his study of the second step thatR os ta nd b eg an h is w ork o n th e p ro ble m o f tra um atic p arth en og en e-sis. Traum atic parth enogene sis by dry sp erm (1924), o r by spermtre ated w ith sodiu m fluoride, g lycerine, alcohol, acetone (1926)wherein certa in positive results seem ed to plead in favor of thepresence in the sperm of fertilizing catalysts (1926). In 1928, hep ub lis he d h is re su lts o n th e catalyseur-noyau ~(catalyzingnucleus)in t ra u ma tic p a rthe no ge n es is .

W ithin this same vein, he made test hybrids among differentspecies of amphibians of the same or different genus, and hediscovered the favorable influ ence o f co oling o n the developm ent ofthese hybrid eggs (gynogenesis) (1933.1934). It was as a resultof these observations that he was drawn to the technique ofgynogenesis: the diploidizing effect of cold was to be the mostrem arka ble result of this w ork.

This diploidizing effect of cold was, in the U SA, dem onstratedcytologically by G. Fankhauser in 1939. The results of Rostandprovided the basis for the work of Fankhauser and his school one xp e ri me n ta l p ol yp lo id y.

It w as a s a pe erle ss p ro fe ss or a nd m i nd -o pe ne r ( eveilleur


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d'esprit ) that Rostand remembers the teachings of MauriceC au llery: ~ In m y y ou th I w ent o ften to b oth of th e lab oratories th atP ro fe ss or C au lle ry s uc ce ssiv ely d ire cte d: firs t. th e v en era ble b uild -ing in the Rue de l'Estrapade. where I studied for my diploma ing eneral em bryo lo gy an d w as o ne o f o nly fo ur cand id ates: later, th atb rig ht an d im po sing b uild in g o n th e B oulevard R aspair (R ostand ,1 96 6). T he E vo lu tion of O rg anized L ife L abo rato ry w as created b ythe city of Paris for Giard in 1888 and the Chair in 1892; thela bo ra to ry o n th e B ou le va rd R asp ail w as b uilt in 1 92 3 (V ire , 1 97 9).

M au rice C aullery (1 86 8-1 95 8). th e successo r of A lfred G iard .cannot be defined as an embryologist. but he had such closerelation s w ith this gen eral b io lo gy d iscip line that on e cann ot av oidm en tio nin g h is n am e (F ig . 4 ). F irs t, b ec au se o f th e p ub lic atio n o f h islectures: Les problem es de fa sexualite (1913) and Les p rogr esr ec en ts d e I 'emb ry olo gi e e xp er imen ta le (1 93 9), and then becau seof his prefaces to em bryological works that have since becom eclassics: the preface to T ra ite d 'emb ry olo gie c ompa ree d es In ve r-tebres by C . D aw ydoff (1928), the preface to the book by his pupil.M . A belo os. en titled La regeneration et fes probfemes de famorphogenese (1932), etc. Other pupils of Caullery who m ade anam e for them selves in biology w ere, for exam ple, E . G uyenot. A .V an de l a nd L .G a llie n.

A lb ert R ay na ud , w ho s tu die d u nd er A .V an de I a t th e U niv ers ity o fToulouse, was recom mended by the latter and by M . Caullery toA ntoine L acassagn e, d irector o f t he L ab oratoire P asteur o n th e R ued'U lm in Paris (Raynaud. 1975). He entered the laboratory inO ctober 1936. and his thesis, Mod ific atio n e xp er im en ta le d e ladifferenciation sexueJ/e des em bryons de souris par action deshormone s and rogene s et oestrogenes (Exper imenta l modi fica t ionof sexual differentiation in m ouse em bryos using androgen hor-m ones and estrogens) published in 1942. m arked a period in theh isto ry o f em bry olog y co ncern in g th e p rob lem s of sex ual m orph o-genesis.

It was in 1931. in the Laboratoire d'evolution des etreso rg an ise s o n th e B ou le va rd R as pa il. a nd a t th e m arin e la bo ra to ryin W im ere ux th at L ou is G allie n b eg an h is s cie ntific c are er. T he re h ew ro te his thesis on a p arasitic T rem atod e w orm , R ec he rc he s e xp e-r im en ta fe s su r /e d im or ph ism e e vo /u tif e t la b io fog ie du Po /y stomuni nt eg er rimum Fro ef (E xp erim en ta l re se arc h o n e vo lu tio na ry d im or-phism and biology of Po/ystomum integerrimum Froe/)(1935) . Thatsame year was decisive for him : 1935 was the year that deter-m in ed m y f inal o rien tatio n. T he p rog ress m ad e in m y stu dies o f t hee nd oc rin olo gy a nd emb ry olo gy o f se x w as, in th is re ga rd , d ec isiv e~(G allien. 1 96 2). T he career of G allien h ad b een decided , an d he w asto becom e one of the m ajor figures in French em bryology.Conclusion

Exp erim en ta l emb ry olo gy w as b orn o f a theory and a method. Thetheory was established by His in 1874 and developed by Rouxduring the 1880s. This w as a theory that saw the entire individualas contained w ithin the egg cell. w ith the successive divisions ofthis cell being nothing m ore than the distribution of the differente lem en ts th at w ou ld g o in to fo rm in g th e in cre asin gly sp ec ia liz ed c elllines th at even tu ally g iv e rise to th e differen t tissu es an d org ans.T his is the m osaic th eory . th e basis of t he m icrom erist theo ries w ithth eir re pre se nta tiv e p artic le s c on ta in ed w ith in th e n uc le us : it is th eor ig in of neo-preformat ionism.

The m ethod was born with t he i ntr oduc ti on o f exper imenta l

Erperimelllal emhryology ill Fran('t' 21

handling of the em bryo or the blastomeres. It was, using theterm inology of Fol and W arynski, the direct m ethod. This m ethodcontrasted w ith the indirect m ethod. w hich was then practiced byDareste. The indirect method consisted in subjecting a wholeem bryo tothe effe ct of a teratogenic a gent. Fo l a nd W aryn ski w ishedto understand the m echanism of em bryonic developm ent: D arestew anted to e ngage in experim ental trans form ation (Fischer. 1986,1987a). Both had adopted a method that responded to thebiological problem posed by them .

This direct method in embryology was applied by Roux, inG erm any. on frog eg gs. and by C hab ry, in F rance , on ascid ian eggs.T he experim ental results spo ke in favor of a neo-prefo rm ation - theegg was a m osaic. But the same method a pp lie d t o t he s ea -u rc hinegg produced converse results: the egg regulated. In other organ-ism s, these n ew em bryolog ists discovered eggs- w ith regula tion:these experiments nurtured the arguments in defence of neo-epigenesis. The debate betw een these two fundam ental theoriesconcerning generation and heredity was set off starting in the18905.

S cientists took up different th eoretical po sitions not only on thebasis of the experim ental m aterial used. but also on the basis ofpersonal id eolog y. O . H ertw ig defended neo-epige nesis: D rieschtook the side of neo-epigenesis in the early 1890s, only to decidein 1896 that neo-preformation was the only theory capable ofexplaining the phenom ena of em bryogenesis. In France, the tend-e nc y is to wa rd s neo-epigenesis, w he re as in t he E ng lis h-s pe ak in gc ou ntr ie s, s cie nt is ts le an to wa rd s n eo -p re fo rm a tio n.

In any case. em bryologists. w ho were to be m ore conciliatorytha n g eneticists a fter 1910 . end ed up adopting both theories. F romR ou xto W olff a nd G allie n, w ith ou t fo rg ettin g D alc q. o ne h ad to a dm itth at th e o nly lo gic al a nd ra tio na l c ou rs e w as to re ac h a re co nc ilia tio nof theories. The result was that the em bryologists continued, asregards theory, to lean towards epigenesis. Thus, epigenesistrium phs in m any regards... If epigenesis m eans that everything isn ot pre form ed, one m ust neverthele ss rem em ber tha t everyth ing isi nd ee d p re pa re d ,

Th. H. Morgan. who began his scientific life in experim entale mb ry olo gy , re fu se d to fo llo w th e th eo re tic al id ea l o f t he g en etic is ts(M organ, 1936). If the geneticists p re fe rre d n eo -p re fo rm atio n toneo-epigenesis, it w as t:ecause they had a reductionist view ofbiological phenom ena. On the other hand. if em bryologists w erea ble to re co nc ile n eo -p re fo rm atio n and neo-epigenesis, it wasbecause th ey c on sid ere d th at b io lo gic al e ve nts c ou ld b e e xp la in edonly through a dualist theory. This is the essential teaching fromembryology.

R e f e r e n c e sA B EL O OS . ~ \. ( 19 32 ). La regeneralion e t les p roblem es de la m orp hog encse . P refaced e M . C au lle ry . G au th ie r- Vil la ir s. P ar is .A NC EL . P . and LALLEMAND,S . (1 928 ). S ur la p rotection contre I'action de s rayo ns X

p ar u ne irra dia tio n p re ala ble (ra dio ph yla ~ie ). C .R . Soc. B io i. 9 9: 1 58 8- 15 90 .A N CE L. P . a nd W O LF F, E . ( 1 93 3) . S ur 1 0'1e alis ati on e ~p en m en ta le d es m on str uo sit es .

C .R . S oc . Bioi. 112: 798.AN CEL. P. and W OLFF. E. (1934). Sur une m ethode teratogenlque dlrecte.. C.R.

S ea nc es A ca d. S ci. 1 99 : 1 07 l.B AL AN . B . ( 19 79 ). L o rd re et Ie tem ps. / ana rom ie com paree et I hlsfoire des ~ Ivan ts

au X/Xe s il k/e . V rln , P ar is .B A LA Z UC , J . ( 19 48 ). L a t ~r al ol og ie des co icopi c re s e t e .p e ri en c es d e t ra n sp la nt at io n

chez T en eb rio m olito r iL .). M em . M us . H ls r. Na t. ( pa ri s) 35 : 1-293.


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. I.L . F ische /BALBIANI, G. (1861). RecherChe sur les phenomenes se~uels des Infusoires. J.

P hyslol. H om me A nim . 4: 102.220, 465-520.BA LBIA NI, G . (1864). Sur la constitution du germ dans I'o cu f a nim al avant la

fecond


13/13

Naud, P a r i s .HE RT W IG ,O . ( 1 89 0) . E xp er im en ta ll e S tu dle n a m ti er es ch cn E i, \ 'o r, w ah re nd u nd n ac h

de r be fruch tung , J ena ls ch e Z ei ts ch r. Na ru rw i ss . 24 : 268- 313 .HORDER,T .J . , WITKOWSKI .J.A. andVI/YlIE,C.C. (Eds.)(1986). A HistoryofEmbryology.Cam b ri dg e Un iv er Sit y P re ss , C am b ri dg e, L on do n, N ew Yo rk .H U AR D, P. a nd M O NT AG NE ,M . ( 1 94 9). A ug us t W eis ma nn (1 83 4-1 91 4) . E xtr . anent

Med. 1 : 289- 304 .JOST , A . ( 1 986 ). R ob ert C ou mer e t Ie ro le d e /'h isto ph yslo lo gle d an s le s o rig in es d eI'endocrmologle. P al ais d e I 'l ns ti tu t. P ar is .

J u b i l e de MonsieurIeProfesseur PolBouin(1946), Arch.Anat. His t. Embrol,30: 109-149.KL EBS ,G .1 18 87 ). U b er de n E in flu ss d es K er ns i n de rZ ell e. B io i. Centralbt. 7: 161-168.KOLLIKER,A, (1882). Embryologle ou T ra tte c om ple t d u d e~ elo pp em en t d e I'h om me

et des anm1aux superieurs. Reinwa ld . Pa ri s .K U LA GI N(1 89 8). U be r d ie F ra ge d er g es ch lec htilic he n V er me hru ng b el d en T ie re n.

Zoo l. An z. 21 : 653- 667 .L EGA IT ,E . ( 1 97 5) . L es s cie nc es m o rp ho lo gi qu es a N an cy . Ann . Me d. N an cy , Special

C en te na lre . 3 0 a rII 19 75 .L OE B, J. (1 89 2). In estigatio n in p h~ sio lo glcal m orph olo gy . III. E xp erim en ts o n

c le a a ge. Journ . Morphol , 7 : 253-262 .LOEB, J. ( 18991 . On t he n at ur e o f t h e p ro c es s o f f er ti li za ti on a nd t he a rt if ic ia l p ro duc ti onof normal larvae (plutei) f r o m t he unfe rt il il ed eggs of t he sea urch in .Amer , Joum.

Physiol. 3 : 135- 138 .M A IE NSCHEIN. J. ( 19 86 ). P re fo rm at io n o r n ew f orma ti on - or neither or both? In AHistory of EmbryologylEds . T ,J , Ho rd er , J .A . W i tk owsk i a nd C ,C , Wy li e) . Camb ri dg e

Un iv er si ty P re ss . C am br id ge , L on do n, N ew Yo rk , p p. 7 3- 10 8.M A R E Y , J . ( 1878 ). La me th od e g ra ph iQuedans l es sCi en ce s e xp er im enr al es e tp ri nc ip al em en r e n p hy sl ol og le e t e n m ed ec me . M as so n, P ar is .M AUBE UGE .P .L . ( 19 73 ). Q u elq ue s a sp ec ts h is to rl qu es d u m o uv em en t s cie nt if lq ue e nLor ra ine , Bul l. A ca d. SOC . L o rr am es S ci , 1 2: 1 -3 2.M ICHEL .A .( 19 02 ). L 'e xp er im en ta tlo n s ur l es p re em b ry on s e t s on im p or ta nc e p ou r l amorpho log le genera le . R ev . S ci . 17 : 456- 462 ,M ORGAN ,T .H . ( 18 99 ), T he a ct io n o f t h e s alt s ol ut io ns o n t he u nf er ti li ze d a nd f er ti liz ede gg s o f A rb acia . an d o f o th er a nim als . Arch. En tw . O rgan, 8 : 448-539 .MORGAN,T ,H . {1936 ). Emb ryo log le e t genet iQue . ( Tr an s. J ea n R os ta nd ). G al lim ar d,

Paris.NUSSBAUM,M.(1886) . U b e r die Theilbarke ltder lebenden r- .1a te r ie . . Ml t the ll :Dies po nt an e u nd k un st li ch e T he il un g d er I nf us or ie n, Arch. m lk r. Anar . 26 : 485- 538 .OPPENHEIMER, J .M . 11967) . E ssa ys in th e H istO ry o f E mb ry olo gy a nd B io lo gy. MI TP re ss , C am brid ge. M as s an d L on do n.PETTIT ,A. (1902) , R ecu ell d es p nn clp ale s o eu ~'fC S d e C h. P ou ch er. p re ce de d 'u ne

noti ce b iographique . M as so n, P ar is .P FE FF ER . W . (1 88 8) . U be r ch em ota ch tis ch e B e e gu ng en \Io n b ac te rie n, F la ge lla te n

u nd V olv ocin em , U nte rs a us d em B ota n. In stitu t IU T ub ln ge n, II.POUCHET .H .G . ( 1893) . L au re nt Chab ry . J. Anat. Phy-slOl.Homme An im . 29 : 735- 739 .P R E N - N T , A.11891). E le me nt s d 'e mb ry ol og le d e I 'H om m e et des Ve rt eb re s. Prefaced u Pr of esseu r Ma th ia s D u va l. G . S te in he il , Pa riS.RAYN -UD.A. \1942). Modificationexpeflmentale de la differenciat ion se,welle desembryons de SOUf iS pa r action de s hormones androgenes et oestrogenes.

E .rfJc rim cJ1 tu / cm hry%gy in F ra ncc 13H erm an n & C le .. P aris.

R A YN AU D , A . ( 19 75 ). O is co ur s p re sid en tie l. Bull. S oc . Z oo l. F r. 1 00 : 1 1-1 9.REY. R. 11989). Generation et heredlte au 18e slecle. In L o rd re des carac te res .Aspects de /'h ere dlte d an s I histo lfe d es sc ie nce s d e J ho mm e. Conferences du

P ala ls d e la D ec ou ve rte o rg an ls ee s p ar J .L . F is ch er. T ex te s re un is et p re se nte s p arC . B en icho u. V rm , P aris, p p. 7-48 .

R O G E R , J . (1971 ). Le s sCiences de la vie da ns 1 8 pen see fram ;alse du Ville siecle,Armand Co li n, Paris.

R OS TA ND , J . ( 19 22 ). N ote s ur I'h ab lta t d es la r.'e s p ae do ge ne tiq ue s d u g en re M la sto rID ip t . Cec idom~ 'dae ), Bull. Soc. entom. Fr . 1922: 89-90.

R O S TA N D , J . ( 19 24 ). Pa th enoge n es e t ra uma ti qu e p ar Ie s pe rm e sec, C .R . S oc . B IO I.90: 931.

R OS TA ND . J . ( 19 26 ). S ur Ie d eu xie me te mp s d e la p arth en og en es e tra um atiq ue . CR .S oc . B io i. 9 4: 8 36 -8 37 .

R OSTANO . J. (1927). D em i-laNes de M ouches obtenues par ligatures des oeufs 12enote). Bull. Soc. entom. Fr . 1 92 7: 2 15 -2 16 .

R OS TA ND , J. (1 92 8). P ro prietes d u c a ta ly se u r- no ya u , e n p ar th enoge ne setraumatique.C.R. S oc . B io i. 98 : 1207 -1208 .

ROSTAND, J . ( 1966) .Homme s d 'au rr ef ol s e t d 'au Jou rd 'hu l. G a ll im a rd . P a ri s.R OU X, W . (1884). Beitrag zur Entwlckelungsmechanik des Embryo. II. Uber die

E ntw ickelu ng de r F rosch eie r be i A ufh ebu ng d er richten den W irku ng d er S ch e re.Breslauer

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