80 Elementary Manual of Zoology. 
(2) The large muscular stomach, which lies in the middle line of 
the body immediately above the mouth. It is attached 
to the shield by powerful muscles, a pair of which are 
visible in front. ‘ 
(3) The pericardial chamber. This is a transparent thin-walled sack 
lying in the middle line immediately behind the stomach. 
Its function is to receive the blood from the gills and to 
pour it into the heart. It contains the heart, from which 
proceed the thin-walled arteries which convey the blood 
to all parts of the body. 
(4), The straight intestine, which can be seen underneath the heart, 
‘ passing from the stomach towards the abdomen. 
(5) The liver, this is a soft mass of little yellowish lobes lying 
on either side of the stomach and ramifying between the 
other organs throughout the greater part of the cephalo- 
thorax. It pours its secretions into the digestive tract 
by ducts which lie behind the stomach, 
In the female see the ovaries, which in November appear as bright 
yellow masses filled with eggs and protruding on each side above the 
liver, Attached to the ovaries area pair of wide thin-walled ducts 
(oviducts), which you can trace on either side passing down towards the 
genital openings on the ventral surface. 
In the male, in place of the ovaries, see a pair of soft white elong- 
ated glands (testes), which pass up on either side between the heart 
and the stomach. Endeavour to trace the ducts which pass downwards 
on either side of the heart to connect the testes with the genital open- 
ings at the base of the legs. 
Carefully remove the whole of the stomach by cutting through the 
intestine behind, the muscles in front and the gullet below. Cut it 
open, wash out the contents, and see the three powerful teeth it con- 
tains. Observe how these teeth work against each other for crushing 
the food. 
Wash out the cavity in the cephalothorax from which the stomach 
has been taken, and cut out as much of the intestine as is visible, 
-so as to see how the liver is connected with it. Cut away the repro- 
ductive organs and any lobes of the liver that remain, 
cut away the tissues which underlie these organs. 
Immediately in front of where the stomach lay, and close to the 
outer wall of the cephalothorax, the students will now be able to make 
out two soft curved white glands which open immediately in front of 
the mouth. These probably correspond with the green glands of the 
cray-fish, in which case they are excretory organs. 
Look for the small white supra-cesophageal nerve ganglion, which 
lies in front of the gullet, and trace the nerves which pass back from it 
taking care not to 
