Embryology. 121 



ture lay within preformed miniature in ever-increasing" 

 minuteness, as if in a conjurer's box. Thus it was 

 computed that mother Eve must have included over 

 200,000 millions of homunculi, or sometimes it was 

 Adam who was made to bear this burden. For, accor- 

 ding to one party, the ovists, e.g. Malpighi, it was the 

 ovum that contained the miniature which had to be 

 unfolded; while according to others, the animalculists, 

 it was the sperm which contained the preformed model. 



The whole chapter is a somewhat lamentable one in 

 the history of embryology, and yet it must be noted in 

 fairness that the preformationist doctrine had a well- 

 concealed kernel of truth within its thick husk of error. 

 There is a certain sense in which the whole future 

 organism is potentially and materially implicit in the 

 fertilized egg-cell; there is a sense in which the germ 

 contains not only the rudiment of the adult organism, 

 but of successive generations as well. But in neither of 

 these senses was preformationism understood by any 

 of its upholders, and to say that the modern preforma- 

 tionists are simply returning to the views of Bonnet and 

 Haller is to misread the history. 



Caspar Friedrich Wolff (1733-1794) was the first to 

 raise a strong protest, not only against the doctrines 

 of the preformationists, but against their Wolff and 

 method of speculating rather than observing. Epigenesis. 

 At the age of twenty-six he published his doctorial 

 thesis, Theoria Generationis (1759), an embryological 

 classic. Appealing to facts, he showed that there was, 

 in the early stages of the chick's development, no visible 

 hint of a preformed miniature, but that the various 

 organs made their appearance successively and gradu- 

 ally, and were to be seen being formed. He was clear 

 that what he saw was a development, a real becoming, 

 a gradual differentiation from apparent simplicity to 

 obvious complexity. And as to this all are now agreed ; 

 it is a fact of observation. 



Theory and difference of opinion begin when we ask 

 how the gradual differentiation of an apparently simple 

 germ or rudiment is to be interpreted; and here, Wolff 

 was in no better position than his predecessors. As 



