THE CHORION. 



377 



briefly call the tufted membrane (cliorioii), is completely 

 covered with small knots or tufts, and forms a globe or 

 sphere of 6-8 millimetres in diameter (Figs. 127-129.) In 

 consequence of the accumulation of a large mass of liquid 

 in the inside, the tufted membrane (choriori) continually 

 increases in size, so that the embryo occupies only a small 

 part of the space within the egg-bladder. At the same time 

 the tufts on the chorion increase in number and size, and 



FIG. 132. Human embryo, with amnion and allantois, in the third week ; 

 with a large globular yelk-sac (below) and a bladder-like allantois (right) ; 

 there are as yet no limbs. The germ and its appendages are surrounded by 

 the tufted membrane (cliorion). 



FIG. 133. Human embryo, with amnion and allantois, in the fourth 

 week. (After Krause.) The amnion (M:) lies pretty close to the body. The 

 greater part of the yelk-sac (d) has been torn away. Behind this the 

 allantois (/) is visible, as a pear-shaped vesicle of considerable size. Arms 

 (/) and legs (6) are just beginning; r, fore-brain; z, twixt-brain; m, 

 mid-brain ; h, hind-brain ; n, after-brain ; a, eye ; /:, three gill-arches j c, 

 heart ; *, tail. 



