256 



THE EVOLUTION OF MAN. 



Fig. 52. 



^ h% tna C 



tti s 



Fir.. 53. 



Fig. 54. 



Fig. 55. 



J/t s / 



Fig. 52. — The ideal Primitive Vertebrate type, seen from the left side : 

 inr, medullary tube; x, chorda; na, nose; au, eyes; g, ear- vesicle ; wd, 

 mouth; k, gill -body ; Is, gill-openings; leg, gill-arches; ma, stomach; I, 

 liver; d, small intestine; af, anus; v, intestinal vein; hz, heart; a, body- 

 artery ; n, primitive kidney canal ; e, ovary ; /(, testicles ; c, bod3'-cavity 

 (visceral cavity); ms, muscles; Ih, leather-skin (corium); oh, outer-skin 

 (epidermis) ; /, skin-fold, acting as fin. 



Fig. 53. — Same as above, viewed from the ventral side. 



