EMBRYOLOGY AND EVOLUTION 



that the body is supernaturally created, as some of the *'pre- 

 formationists" did in the eighteenth century. This old doc- 

 trine of preformation, or "evoiutio," as it was called, main- 

 tained that the fully-formed but minute organism was 

 encased within the egg or sperm, and the microscopists of 

 the day, with poor instruments but good imagination, thought 

 they could see the "homunculus," or little man, neatly packed 

 away within the human germ cell. Within this homunculus 

 in turn it was held that there must be another generation 

 of germ cells, each containing its homunculus, and so on 

 ad infmitum. Thus arose the doctrine of infinite encasement, 

 or "box in box," and as the schoolmen of the Middle Ages 

 discussed how many angels might stand on the point of a 

 needle, so their successors of the eighteenth century dis- 

 cussed how many fully formed but infinitely minute genera- 

 tions might have been contained in the ovary of Mother 

 Eve. These speculations reached their culmination in the 

 works of Charles Bonnet (1748-1773), the distinguished 

 natural philosopher of Geneva, in which he denied all new 

 formation, all development or generation, and held that in 

 the original creation of the progenitor of each species God 

 created at one stroke all the individuals that would ever 

 come from that progenitor. Thus every individual in the 

 world was supernaturally created. 



The actual study of the development of eggs forever put 

 an end to such speculations. Caspar Frederick Wolff (1759) 

 demonstrated that fully formed but minute organisms are 

 not contained in germ cells; that development is not a mere 

 unfolding of that which is already infolded, but that it con- 

 sists, from inception to maturity, in an increase of com- 

 plexity; and though he over-emphasized the simplicity of the 

 germ, no one now questions that individual development 

 everywhere consists of progress from a relatively simple 



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