344 Everard Home on the changes the egg undergoes 
vessels, one to the right side of the abdomen of the embryo, 
the other to the left, sending branches over the whole of the 
areolar membrane, which was bounded on each side by a 
large trunk carrying red blood ; but the two trunks did not 
unite, there being a small space on one side rendering the 
circle incomplete. 
The vesicle was somewhat increased in size ; it lay in the 
lower part of the abdomen, the parietes of which were not yet 
formed. Plate XXXV. fig. 1,2,3. 
In 3 days, the outer areola had extended itself over of the 
circumference of the yelk, carrying the marginal arteries 
along with it to the outer edge, but diminished in size. The 
brain was much enlarged, consisting of four cavities contain- 
ing a fluid, the cerebellum still the largest. The spinal mar- 
row and its nerves were more perfectly formed. The eye 
appeared only to want the nigrum pigmentum. 
The right ventricle of the heart contained red blood : the 
arteries could be traced to the head : the rudiments of the 
wings and legs were formed : the vesicle was farther en- 
larged, but its vessels did not carry red blood. It had forced 
its way out through the external covering of the yelk, and 
opened a communication through this slit, by which a part of 
the albumen was admitted to mix itself with the yelk, and 
give it a more oval form. At this period the embryo is 
generally found to have changed its position, and to be 
wholly turned on the left side. Plate XXXV. fig. 4, 5, 6. 
In 4 days , the vesicle was more enlarged and more vascular, 
its vessels containing red biood. 
The optic nerve a? d nigrum pigmentum of the eye were 
yisible ; the other parts had become more perfectly formed. 
