Facts and Factors of Development $7 



1. Preformation. — When the mind is once lost in the mystery 

 of this ever-recurring miracle it is not surprising to find that 

 there have been those who have refused to believe it possible and 

 who have practically denied development altogther. The old doc- 

 trine of "evolution," as it was called by the scientists of the 

 eighteenth century, or of preformation as we know it to-day, 

 held that all the organs or parts of the adult were present in the 

 germ in a minute and transparent condition as the leaves and 

 stem are present in a bud, or as the shoot and root of the little 

 plant are present in the seed.* In the case of animals it was 

 generally impossible to see the parts of the future animal in the 

 germ, but this was supposed to be due to the smaller size of the 

 parts and to their greater transparency, and with poor micro- 

 scopes and good imaginations some observers thought they could 

 see the little animal in the egg or sperm, and even the little man, 

 or "homunculus," was described and figured as folded up in one 

 or the other of the sex cells. 



This doctrine of preformation was not only an attempt to solve 

 the mystery of development, but it was also an attempt to avoid 

 the theological difficulties supposed to be involved in the view 

 that individuals are produced by a process of natural develop- 

 ment rather than by supernatural creation. If every individual 

 of the race existed within the germ cells of the first parents, then 

 in the creation of the first parents the entire race with its millions 

 of individuals was created at once. Thus arose the theory of 

 "emboitement," or infinite encasement, the absurdities of which 

 contributed to the downfall of the entire doctrine of preformation, 

 which, in the form given it by many naturalists of the eighteenth 

 century, is now only a curiosity of biological literature. 



2. Epigcncsis. — As opposed to this doctrine of preformation, 

 which was founded largely on speculation, arose the theory of 



* The little plant in the seed is itself the product of the development of 

 a single cell, the ovum, in which no trace of a plant is present, hut of course 

 this fact was not known until after careful microscopical studies had been 

 made of the earliest stages of development. 



