GASTEROPODS 341 
VITAL ORGANS, STOMACH, LIVER, RENAL GLANDS, ETC. 
The digestive tract will be found to widen out a short distance 
back into a crop or stomach, and, continuing still further, to lose. 
itself in a soft, brownish mass within the coiled spire, which is the 
liver. The very large size of the liver leads one to suspect that 
Fulgur and Buccinwm must be voracious creatures to need so large 
an organ for the secretion of bile. In many species of mollusks 
the stomach and intestines are filled quite solidly, at times, with a 
gelatinous transparent substance called the crystalline stylet. Just 
why the digestive tract should be clogged with this substance no 
one has yet been able to explain, so here again is a chance for 
original investigation. The intestine curves about after reaching 
the liver, and comes forward again to appear once more as the 
rectum, clinging to the inner surface of the free portion of the 
mantle. 
Closely associated with the liver, but differing slightly in color, 
is the gonad, or organ in which the genital products are formed. 
Situated dorsally and forward of the liver and gonad is a large 
renal gland, which may readily be detected by its peculiar struc- 
ture. In some forms the kidney is closely associated with the 
gonad, and seems to codperate with the latter in the generative 
functions. 
HEART AND VASCULAR SYSTEM 
To find the heart, make an incision into the body just at the 
posterior end of the gills. The heart is white and round, and is 
inclosed within a cavity known as the pericardium ; it has a ven- 
tricle and one or two auricles, although in Buccinum and Fulgur 
there is but one auricle. 
There is nothing remarkable about the vascular system to dis- 
tinguish it from that of many higher forms of animals. It is, 
however, not completely closed—by which is meant that the blood 
is not always contained within arteries or veins, and that it does 
sometimes flow into other organs and floods certain other body- 
cavities, although the vascular system of mollusks is by no 
means so completely open as is that of insects and crustaceans. 
