222 THE EVOLUTION OF MAN. 



same rudimentary form. We need only compare the em- 

 bryos of these various classes of animals at corresponding 

 stages of development, in order to assure ourselves of this 

 fundamental fact. (Of Plates VI. and VII., second cross- 

 line.) 



PiQ. 227. — Brains of three embryonic Sknlled Animals in vertical longi- 

 tudinal sections: A, of a Shark (Heptanchus) ; B, of a Snake (Coluber); 0, of 

 a Goat (Copra,) ; a, fore-brain ; 6, twixtibrain ; c, mid-brain ; d, hind-brain ; 

 e, after-brain ; s, primitive fissnre of the brain. (After Gegenbaur.) 



Fig. 228. — Brain of a Shark (ScyUium) from the dorsal side : g, fore- 

 brain ; h, olfactory bulbs of the fore-brain, which send the large olfactory 

 nerves to the large nose capsules (o) ; d, twixt-brain ; 6, mid-brain (behind 

 it, the insignificant rudiment of the hind-brain) ; a, after-brain. (After 

 Busch.) 



Fig. 229. — Brain and dorsal marrow of a Frog : A, from the dorsal side ; 

 B, from the ventral side ; a, olfactory bulbs, in front of the fore-brain (!)) ; 

 i, funnel at the base of the twixt-brain ; c, mid-brain ; d!, hind-brain ; s, 

 rhomboid groove in the after-brain ; m, dorsal marrow (very short in the 

 frog) ; m', root-processes of the spina! nerves ; t, fibre at the end of the 

 dorsal marrow. (After Gegenbaur.) 



