256 



THE EVOLUTION OF MAN. 



^ji "^ nir l^j fj; h 



Fig. 52. 



/ 



Fig. 53 



m f 



Fig. 54. 



Tit S t 



Fig. 55. 



tivs ^ 



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

 ynr, medullary tube ; x, chorda ; na, nose ; au, eyes ; g, ear-vesicle ; nxd, 

 mouth; t, gill -body; lis, gill-openings; leg, gill-arches; ma, stomach; I, 

 liver ; d, small intestine ; of, anus ; v, intestinal vein ; /is, heart ; a, body- 

 artery ; n, primitive kidney canal ; e, ovary ; h, testicles ; c, body-cavity 

 (visceral cavity) ; ws, muscles ; lli, leather. skin {corium') ; oh, outer-skin 

 [epidermis) ; f, skin-fold, acting as fin. 



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



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