I EMBRYOLOGICAL ARGUMENT 35 



The development of the central nervous system 

 furnishes us with another important argument out of 

 many in favour of evolution. The brain of man, dur- 

 ing the development of the embryo, passes through a 

 series of stages of increasing complexity, and a careful 

 study shows that these stages, which are temporary in 

 the embryo, are permanent in the principal groups of 

 animals. One may easily detect in the evolution of 

 the human brain a stage corresponding to that of the 

 brain of fishes ; but while the fishes permanently re- 

 tain this brain-structure, an advance occurs in man, 

 and the brain acquires the characters of the reptilian 

 encephalon ; later on it progresses again, and acquires 

 bird characters, then mammalian characters, and 

 finally it acquires those characters which are peculiar 

 to mankind. Here again, ontogeny demonstrates phy- 

 logeny, and phylogeny, that is, derivation from the 

 lower vertebrate forms, must be admitted to be true, 

 unless some better explanation can be proposed. 



Many other embryological facts do not admit of 

 any explanation, if the hypothesis of derivation and 

 descent is not admitted. For instance, on the special 

 creation theory, why have baleen whales been provided 

 with a full set of teeth' which remain rudimentary, and 

 soon disappear in the course of development, and 

 which are never used nor even could be useful ? Again, 

 why are there pelvic bones in the whale, and even 



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