THE GERM-PLASM THEORY 73 



cell) a simple substance, or has it an architecture, 

 so to speak, of its own ? Simple in chemical com- 

 position it is not, for dead nuclein, which is, of 

 course, the only kind which can be examined, has 

 a complicated chemical formula. But is it other- 

 wise simple or indifferent ? To put the matter 

 plainly, if a little crudely, suppose we could divide 

 the chromatin up into its ultimate units not 

 chemical but vital always supposing that it 

 consists of such units, would all these units be like 

 to one another and capable, in case of necessity, 

 of replacing one another ? Or, on the other hand, 

 would each have its own characteristics, as the 

 cells of the human body have each their own 

 characteristics and functions ? Such is the guise 

 under which the old question of preformation or 

 epigenesis now presents itself to us. To the pre- 

 formationists or evolutionists, as they were then 

 called of the eighteenth century, unacquainted 

 with the knowledge which the microscope has 

 given us of the germ cells, the germ was almost a 

 miniature of course an extremely minute mini- 

 ature of the adult form, and its development 

 was merely an unfolding of already existing parts. 

 Bonnet, who was the protagonist of this theory, 

 did not hold that his miniature model was exactly 

 like the perfect animal, but taught that it con- 

 sisted of " elementary parts " only, which he 

 thought of as a net, whose meshes were filled up, 

 during development, and by means of nutrition, 

 with an infinite number of other parts. 



On the other hand the supporters of epigenesis 

 the first of whom was K. von Wolff , held that there 



