THE EVOLUTION OF MAN. 



368 



ments of the higher sense-organs, and the rudiments of tho 

 gill-openings, piercing the sides of the neck (Fig. 122, III. ; 

 Plate VII. Fig. M I.). The allantois has growr out from the 



FIG. 122. Human germs or embryos from the second to the fifteen! h 

 week (natural size), seen from the left side, the arched back turned towards 

 the right. (Principally after Ecker.) II., human embryo of 14 days ; III., of 

 3 weeks; IV., of 4 weeks; V.,of 5 weeks ; VI., of 6 weeks; VII., of 7 weeks: 

 VIIL, of 8 weeks ; XII., of 12 weeks ; XV., of 15 weeks. 



hind end of the intestine. The embryo is already entirely 

 enveloped by the amnion, and is now only connected with 

 the germ-vesicle, which is changing into the yelk-sac, by 

 means of the yelk-duct, in the centre of the abdomen. 



