a 
, 
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Description of a Species of Caligus. 257 
ed any blood in the stomach of these animals, although we have 
often examined them, immediately on taking them from the fish. 
On the contrary, the fluids always have a light color. 
We have not fully satisfied ourselves of the nature of its food, 
but presume that it lives on the mucus which covers the body of 
the fish. The mucus is one of the natural secretions of the fish, 
and is always abundant. The organs of the mouth are well 
formed for the collection of it, and the free motion in the whole 
buccal mass seems peculiarly fitted for this purpose. 
Several specimens of the Caligus, when confined on their 
backs in but a small portion of water, just sufficient to cover them, 
have been observed to elevate the buccal mass, and take in glob- 
ules of air, which passed down the esophagus into the stomach, 
and thence through the intestine. Occasionally the globules of 
air have been so numerous and taken in such rapid succession, as 
to fill the stomach, and very much inflate it. In their passage 
through the esophagus they usually stop for a short time at the 
entrance to the stomach, indicating the existence of a valve or 
sphincter at this place. 
b. Circulation. 
The blood of the Caligus, as in other Articulata, is a limpid 
fluid, containing suspended in it numerous minute colorless par- 
ticles. These particles are ge) various in their form and size. 
The smallest scarcely equal ;,';; of an inch. bes have ob- 
served one particle the length of which was about ;1, of an inch, 
and its breadth } its length ; another had nearly the same length 
anda breadth equal to 4 its length. These particles can accom- 
modate themselves to the size of the passage through which the 
blood is flowing, becoming narrow and elongated if the passage 
is narrow, and again resuming their former proportions when they 
have reached a free open space. 
The circulation in the Caligus is wholly lacunal; it appears to 
consist of broad irregular streams, passing through the spaces left 
among the internal organs, and in no part have we discovered dis- 
tinct vessels. 'These streams have in general definite directions, 
yet are seldom uniform, continuous currents. ‘They mostly ad- 
vance by successive vibrations, depending on the palpitating action 
of the body. A single centre of circulation, or a heart, this ani- 
mal can scarcely be said to possess. There are two points in the 
medial line where there is a valvular action, and each has its 
Vou. XXXIV.—No. 2. 33 
