PROBLEM OF DIFFERENTIATION 3 



to have (and which certain over-enthusiastic observers claimed to 

 have seen through their microscopes ; see Cole's Early Theories of 

 Sexual Generation) only required to increase in size, as if inflated by 

 a pump, in order to produce development. Instead of regarding 

 the rudiments of the organs as being preformed in their definitive 

 adult positions, Bonnet imagined them as "organic points" which 

 subsequently had to undergo considerable translocation and re- 

 arrangement. He was thus able to reconcile his belief in preforma- 

 tion with the empirical fact that the germ or blastoderm of the early 

 chick showed no resemblance to a hen. 



Bonnet's theories were ahead of his facts, and, indeed, he seems 

 to have been proud of it, for he refers to the preformationist view 

 as " the most striking victory of reason over the senses ". The hypo- 

 thesis of such an invisible and elastic preformation was perhaps 

 permissible in Bonnet's day, but later observational and experi- 

 mental evidence has rendered it utterly untenable. Further, a rigid 

 preformationist view which asserts that the &gg is a miniature and 

 preformed adult, necessarily implies that the egg must also contain 

 the eggs for the next generation ; the latter eggs must therefore also 

 contain miniature embryos and the eggs for their subsequent 

 generations. Bonnet realised that an emboitement or encasement of 

 this kind ad infinitum would be an absurdity. (Incidentally, it may 

 be noticed that if it were true, phylogenetic evolution — unless it too 

 were preformed and predetermined — would be an impossibility.) 

 But then, if all subsequent generations are not preformed in minia- 

 ture now% there must come a time when they are determined and 

 preformed. Before this time they were neither determined nor 

 preformed, and this making of a new determination, albeit pushed 

 into the future, is the antithesis of preformation. 



If pushed to its extreme conception of infinite encasement, then 

 preformation is absurd ; if not pushed to this extreme, preforma- 

 tion will not account for the determination of ultimate future 

 generations ; and if it did apply, preformation would be an unsatis- 

 factory view in that it assumes that the diversity which is progres- 

 sively manifested in development is ready-made at the start, and 

 in no way attempts to explain it causally or to interpret it in simpler 

 terms. 



