368 THE EVOLUTION OF MAK. 



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

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

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



FIG. 122. Human germs or embryos from the second to the fifteenth 

 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; 

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



hind end of the intestine. The embryo is already entirely 

 envelope (J 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. 



