ONTOGENESIS 191 



is different from that of the other. More funda- 

 mental is the question : Why does the shapeless germ 

 take form at all? Nothing that we can learn of 

 its nature or its structure gives us any reason for 

 believing, a priori, that it will shape itself into an 

 individual that resembles its parents. This is an 

 old problem, and its solution was attempted long 

 before our modern instruments for research gave us 

 the insight into developmental processes we now 

 possess. 



Preformation. Suggested perhaps by the struc- 

 tures found within the flower-bud, or the insect 

 chrysalis, the idea was long current that the germ 

 contains within itself the whole organism in minia- 

 ture and that development consists, simply, in an 

 unfolding and enlarging of this preformed indi- 

 vidual. The chief elaborator of this speculation was 

 Bonnet (1720-1793), but such a great naturalist 

 as Cuvier also subscribed to the doctrine. 1 Since 

 the generation " A " was preformed in the genera- 

 tion " B," then its descendants must also have been 

 there preformed, and so on. The germ-plasm, 

 therefore, was conceived of as a sort of nest of Chinese 



1 There was a division of opinion as to whether the preformed indi- 

 vidual existed in the egg or in the sperm. Some held that the former is 

 the case and that the function of the sperm is merely to fructify or "fer- 

 tilize" the dormant egg. These speculators were denominated "ovists." 

 On the other hand the " animalculists " contended that the egg is merely 

 dead matter serving for nourishment, whereas the sperm is active and 

 "alive." Moreover, with the primitive microscopes of the time, they 

 had no difficulty in distinguishing head, arms, legs, and other structures 

 in the sperm. 



