1876.] The Lobster ; Its Structure and History. 399 
The internal anatomy is best studied by removing part of the 
carapace and tergal portions of the abdominal segments, as 
shown in the plate, taking care not to injure the underlying or- 
gans. Beneath the shell will be found a reddish membrane, 
which must also be carefully removed. The heart will be seen 
to be an irregular hexagonal body, lying just behind the suture 
noticed in speaking of the carapace. It consists of a single ven- 
tricle contained in a sac improperly called the pericardium. It 
gives off in front an artery to the eyes and anterior part of the 
body. Close to this on each side is the hepatic artery. On the 
under side is the sternal artery, while from the posterior angle 
arises the artery which supplies the abdomen. The sternal 
artery connects with one which runs the length of the body on 
the under side. Respiration is carried on in the gills. The 
heart forces out through these various arteries the blood, which 
collects in a venous sinus, passes to the gills, and then back to 
the heart. 
In front of and surrounding the heart is a delicate, convoluted 
mass, the liver, which occupies a large proportion of the thoracic 
cavity. In it are imbedded two elongated bodies, ovaries or 
testes, according to the sex, which pass under the heart. They 
are connected in front of the heart. Behind this connection are 
the oviducts of the female or vasa deferentia of the male. 
The mouth, the position of which has been noticed, is con- 
nected with the cesophagus, which in turn empties into the stom- 
ach. This latter is a large sac in the anterior part of the body, 
and consists of anterior and posterior (cardiace and pyloric) 
portions. In the cardiac is a complex calcareous organization 
Operated by powerful muscles, the office of which is to finish the 
mastication of the food. In the pyloric portion is a ciliated 
strainer. The intestine is a straight tube extending beneath the 
heart from the pylorus to the anus, which is situated on the un- 
der side of the telson. At the base of each antenna is the “ green 
gland,” supposed to be a kidney ; it communicates with the ex- 
terior by an opening in the protopodite. 
The “ brain ” is found at the base of the rostrum, between the 
eyes. It gives off nerves to the eyes, the antennulz and the an- 
tennæ. From the posterior portion are given off two commis- 
sures, which pass around on either side of the cesophagus and unite 
Ma ganglion behind. To examine this and the succeeding tho- 
racic ganglia, it will be found necessary to carefully break down 
Part of the sternum. From each of the esophageal commissures 
