260 ON GENERATION. 



black points. The pupils of the eyes are distinguished ; the 

 eyelids appear, as does also the membrana nictitans in the 

 greater canthus of the eye, a membane which is proper to birds, 

 and which they use for cleansing the eyeball. The convolutions 

 of the brain farther make their appearance ; the cerebellum is 

 included within the skull ; and the tail acquires the charac- 

 teristic shape of the bird's rump. 



After the fourteenth day the viscera, which up to this time 

 have been white, gradually begin to assume a flesh or reddish 

 colour. The heart, having now entered the penetralia of the 

 thorax and been covered with the sternum, inhabits the dwelling 

 place which itself had formed. The cerebrum and cerebellum 

 acquire solidity under the dome of the skull ; the stomach and 

 intestines, however, are not yet included within the abdomen, 

 but, connected with the parts within, hang pendulous externally. 



Of the two vessels that proceed from the abdomen to the 

 umbilicus, near the anus, one is an artery, as its pulse proclaims, 

 and arises from the arteria magna or aorta, the other is a vein, 

 and extends from the vitellus by the side of the intestines to 

 the vena portse, situated in the concave part of the liver. The 

 other trunk of the umbilical vessels, collecting its branches 

 from the albumen, passes the convexity of the liver, and enters 

 the vena cava near the base of the heart. 



As all these things go on becoming clearer from day to day, 

 so the greater portion of the albumen is also gradually consumed; 

 this, however, is nowise the case with the vitellus, which remains 

 almost entire up to this time, and indeed is seen of the same size 

 as it was the first day. 



In the course of the following days five umbilical vessels 

 are conspicuous ; one of these is the great vein, arising from 

 the cava above the liver, and distributing its branches to the 

 albumen ; two other veins proceed from the porta, both having 

 the same origin, and run to the two portions of the vitellus, 

 which we have but just described ; and these are accompanied 

 by two arteries arising one on either side from the lumbars. 



The chick now occupies a larger space in the egg than all 

 the rest of the matter included in it, and begins to be covered 

 with feathers ; the larger the embryo grows, the smaller is the 

 quantity of albumen that is present. It is also worthy of ob- 



