345 
during incubation in the common jowl. 
The outer areola had extended itself half over the yelk, 
which had now become still more encreased in size, a greater 
portion of albumen having become mixed with it. Plate 
XXXV. fig. 7,8,9. 
In 5 days, the membranous bag that formed the vesicle 
had acquired a great size, and become exceedingly vascular 
in its coats ; the cavity contained a fluid. The yelk had be- 
come thinner in its consistence, more of the albumen having 
been mixed with it. Plate XXXVI. fig. i, 2, 3. 
In 6 days, the vascular membrane of the areola had ex- 
tended farther over the yelk. The vesicle at this time had 
suddenly expanded itself in form of a double night-cap over 
the yelk and its coverings, beginning to enclose the embryo. 
This change is so rapid, that it has been with difficulty de- 
tected, and different accounts have been given of the mode in 
which it takes place. 
The amnion contained water, in which the embryo floated, 
suspended by the vessels supplying the areolar and vesicular 
membrane. 
The brain had become enlarged to the size of the body of 
the embryo : its vessels were distinctly seen. The two eyes 
equalled in size the whole brain : the marsupium was seen 
covered with nigrum pigmentum. The vessels of the cere- 
bellum could be traced into the convolutions of the pia 
mater. 
The parietes of the thorax and abdomen had begun to 
form ; the wings and legs were nearly completely formed, 
as well as the bill. At this period muscular action was first 
noticed. Plate XXXVI. fig. 4, 5, 6. 
In 7 days, the vesicle having extended over the embryo, 
mdcccxxii. Y y 
