ZOOLOGICAL EXERCISES, 
Notice the blood vessels and lymphatics of the absor- 
bent system on the mesentery which supports the 
intestine ; and the white fat masses on the peritoneal 
folds. Cut the cesophagus and the rectum near the 
anus, and remove the alimentary system to a saucer 
of water, cutting the mesentery with scissors. 
6. Go over the different parts again. Cut open the 
stomach and gizzard longitudinally and notice the 
internal folds. Examine a portion of the mesentery 
with the microscope. The high power will show, if 
the animal has not been dead too long, that the 
vessels on it are ciliated. 
7. Circulatory system.—Examine the heart; it lies in 
the throat, just under the gills. Itis divided into 
three portions; the anterior is white—the bulbus 
arteriosus ; next to it is the ventricle, red and angular ; 
above the ventricle is the awricle, dark red in colour, 
owing to its being full of clotted blood. Trace the 
aorta torward. It divides into two branches, one 
going to each set of gills. The heart is, therefore, 
respiratory, and not systemic as in the invertebrates. 
The rest of the circulatory system can only be made 
out by injecting the vessels, a process which requires 
much practice and expensive apparatus. 
8. Reproductive system.—Consists of two long tubes, 
bluish-white in colour, more or less swollen according 
to season,and lying along the upper part of the visceral 
cavity, just below the air bladder. Examine a portion 
with the microscope, and observe the sex. 
9. Renal system.—Cut open the air bladder, if it has not 
been ruptured before. It is large, extending the 
whole length of the abdominal cavity, and simple. 
The membrane is so thin that on its dorsal surface 
