45: 



THE EVOLUTION OE MAN. 



Lh E, 



■/ Lh 



Figs. 158-lGO. — Transverse section through an early larval form of 

 Amphioxus. (Diagrammatic, after Rolph.) (Cf. Fig. 152, p. 424.) In Fig. 

 158 there is a free passage from without into the intestinal cavity (I>), 

 thi-ough the gill.opcnings (Zi). In Fig. 159 the lateral longitudinal folds 

 of the body-wall, the gill-roof, are forming, growing downwards. In Fig. 

 160 these side-folds have grown towards each other and their edges liave 



