I INTRODUCTORY 15 



Malpighi in the memoir, ' De formatione pulli in ovo/ which he 

 presented to the Royal Society of London in 1673, it was not 

 only adopted by biologists of prestige, by Swammerdam, Haller, 

 who in his early days had been an advocate of Epigenesis, de 

 Buffon, and Bonnet, but secured the adherence of philosophers 

 of such eminence as Malebranche and Leibniz. 



In some cases it was accepted as a result of observation. Thus 

 Malpighi, 1 in the treatise referred to, asserted that he had himself 

 observed the chick in the unincubated egg, ' inclusum foetum 

 animadvertebam, cuius caput cum appensae carinae staminibus 

 patenter emergebat,' while de Buffon 2 expresses himself even 

 more categorically. ' Fai ouvert/ he says, ' une grande quantite 

 d'ceufs a differens temps, avant et apr&s 1'incubation, et je me 

 suis convaincu par mes yeux que le poulet existe en entier dans 

 le milieu de la cicatricule au moment qu'il sorte du corps de la 

 poule/ To others, however, it was rather a matter of theoretical 

 necessity. Haller explains his conversion from the contrary 

 opinion by asking the very pertinent question, 'Cur vis ea 

 essentialis quae sit unica tarn diversas in animali partes semper 

 eodem loco, semper ad eundem archetypum struit; si materies 

 inorganica mutabilis et ad omnem figuram recipiendam apta est ? 

 Cur absque ullo errore ex gall in ae mista materie ea vis semper 

 pullum, ex pavone pavonem fabricatur ? ' 



'Nil nisi vis dilatans et progrediens recipitur. Ab ea nihil 

 sperarem nisi vasorum rete tamdiu continue amplius futurum 

 quamdiu vis expandens resistentiae superandae par est. Cur loco 

 eius retis cor, caput, cerebrum, ren strauntur ? Cur in singulo 

 animali suus ordo partium? Ad eas quaestiones nulla datur 

 responsio,' a charge which is, of course, perfectly just. 3 



Bonnet's argument is different. The heart of the chick, he 

 points out, is already present in the egg; and since anatomy 

 teaches that all the parts of an animal ' doivent avoir toujours 

 coexist^ ensemble ', preformatioh follows as a matter of course. 4 



The belief in preformation continued paramount till towards 

 the end of the eighteenth century, nor was it till the publication 



1 Malpighi, 1. c., p. 4. 2 de Buffon, 1. c., p. 351. 



3 Haller, 1778, VIII. i. 29, p. 121. 



* Bonnet, Cont. de la nat., 7 me partie, c. ix ; (Euvres, vol. iv, p. 261. 



