2 5 6 



THE EVOLUTION OF MAN. 



FIG. 53. 



FIG. 54. 



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

 mr, medullary tube ; x, chorda ; na, nose ; au, eyes ; g, ear-vesicle ; md, 

 mouth ; k, gill.body ; ks, gill-openings ; kg, gill-arches ; ma, stomach ; I, 

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

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

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

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



FIG. 53. Same as above, viewed from the ventral side. 



