100 Trans. Acad. Sci. of St. Louis. 



traordinarily small size in the egg. The entire organism was 

 therefore held to be preformed in every particular in the Qgg, 

 but in miniature. The germ was likened to the plant bud 

 which contains all the parts of the future flower, petals, 

 stamens, etc., and just as the bud gradually increases in size 

 and suddenly expands into the flower, so also in the develop- 

 ment of animals it was believed that the already present but 

 minute and transparent parts of the animal germ grow, ex- 

 pand and become visible. This doctrine was called the theory 

 of Evolution, or Unfolding, but a later and better name was 

 the theory of Preformation. The essence of the theory is 

 that at no time in development is anything formed anew, but 

 that every part of the organism is preformed in its complete- 

 ness and present from the beginning in the germ. ** There 

 is no such thing as becoming " (or coming into being), says 

 Haller, one of the great upholders of early preformation, 

 * ' no part in the animal body was formed before another ; all 

 were created at the same time.'* It logically followed, and 

 indeed was formulated by Bonnet and others, that in every 

 germ the germs of all subsequent offspring must be included, 

 since living things are developed from one another unin- 

 terruptedly ; this was called the Einschachtelungslehre, or the 

 theory of emboitement, and its adherents actually attempted 

 to estimate the number of human germs which must have been 

 present in the ovary of Eve, accordingly reaching the number 

 200,000 millions. 



But difficulty arose in the ranks of the preformationists 

 upon the discovery of the spermatozoon, and the question 

 soon came to be fervently discussed whether the egg or the 

 seminal filament was the preformed germ. Some, the Ovists, 

 declared in favor of the egg^ others, the Animalculists, cham- 

 pioned the spermatozoon, the latter imagining that with the 

 aid of their magnifying glasses they could see in the human 

 spermatozoon the head, arms and legs of the man, and re- 

 garding the egg merely as a nutritive soil in which the growth 

 of the spermatozoon takes place. 



In 1759, however, Caspar Friedrich Wolff opposed the 

 preformation-theory and maintained that ** at the beginning 

 the germ is nothing else than an unorganized material, elim- 



