532 



THE THEORY OF EVOLUTION 



A. FISH 



OL.L 



CBM 



OP.L 



B. AMPHIBIAN 



DIEN 



OP.L 



D.BIRD 



OP.L 



OL.L 



E.UAMMAl 



CBM 



CBL 



F.HUMAN — "S^rt" 



Fig. 288. — Evolution of the brain in 



vertebrates as suggested by comparative 



anatomy of adult structure (c/. Fig. 39, 



p. 67). 



in human embryos as in other 

 vertebrates (Fig. 287). The 

 tail is noticeably developed 

 in the embryo but becomes 

 rudimentary in the adult. 

 The entire body is covered 

 with a well-developed coating 

 of hair at one stage of the 

 fcetal hfe. The grip in the 

 hands of a young infant is 

 beheved to be a survival of 

 the muscular functions present 

 in our ancestors at birth and 

 necessary for holding to the 

 body of the parent, just as it 

 happens that a young colt 

 must have a muscular system 

 that enables it to run with its 

 mother a few hours after it 

 is born. The great anatomist, 

 Wiedersheim, said that there 

 are at least one hundred and 

 eighty vestigial structures of 

 this kind in the human 

 embryo. These facts of struc- 

 tural resemblance are sum- 

 marized by the classification 

 of man in a family Horninidce 

 which is placed next to the 

 Simiidse, or tailless apes, 

 among the Primates. 



Physiological Evidences. — 

 Functional resemblances have 



In their early embryonic stages the 

 brains of reptiles, birds and mammals 

 show relatively less development of the 

 cerebrum, and thus resemble the adult 

 brain in a fish or an amphibian. CBL, 

 cerebellum; CBM, cerebrum; DIEN, 

 diencephalon; MD, medulla; OL.L., 

 olfactory lobe; OP.L., optic lobe. 



