120 The Science of Life. 



the germ to be an actual miniature of the organism, 

 though his words sometimes convey this impression, but 

 he postulated that the germ " contained tres en petit the 

 elements of all the organic parts". He assumed, he 

 says, "as a fundamental principle, that nothing is gen- 

 erated, and that what we call generation is but the 

 simple development of what pre-existed under an in- 

 visible form, and more or less different from that which 

 becomes manifest to our senses". He thus excludes all 

 new formation or epigenesis. 



To this main hypothesis two subsidiary ones were 

 added: (a) the doctrine ofemboitement, according to which 

 the germ contains the preformation not of one organism 

 alone but of successive generations; and (b) the hypo- 

 thesis of the dissemination of germs scattered through- 

 out the organism, and capable of developing into buds, 

 replacing lost parts, and so forth. As surely as Harvey 

 overshot the mark in one direction, and made develop- 

 ment magical by failing to credit the ovum with a heri- 

 tage of organization, so surely did Bonnet overshoot 

 the mark in the opposite direction, by a theory which 

 amounts to a denial of development altogether. His 

 greatest service was in presenting a reductio ad absur- 

 dum of the extreme preformationist position. 



Bonnet was supported in his extraordinary "system 

 of negations", as Whitman terms it, by the authority 

 of the renowned physiologist Albert von Haller. The 

 latter started as a believer in epigenesis, but was some- 

 how led by his studies on the development of the chick 

 to a complete confidence in the truth of preformation. 

 A single sentence, " Es gibt kein Werden There is no 

 Becoming", sufficiently indicates his position. 



Throughout the seventeenth and eighteenth centuries 

 almost all embryological thinking was dominated by 

 this preformationist creed, and many of the disciples 

 were even cruder than their two masters, Bonnet and 

 Haller. All development was an illusion, it was really 

 only an unfolding (evolutio) of a preformed miniature. 

 Moreover, the germ contained not only a preformation 

 of the organism into which it was destined to grow, but 

 of successive generations as well. Preformed minia- 



