-^340 CRUSTACEA. 



distinguished their ducts, neither have we by dissections obtained 

 more than one of them separate from the body. They are possibly 

 urinary glands. 



The Caligi have heretofore been supposed to live by sucking the 

 blood of the fish on which they are found. It is however apparent, 

 from the structure of the mouth, that they are wholly unfitted for this 

 mode of life. There is no organ which can perform the functions of a 

 sucker. Moreover, we have never detected 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 colour. 



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 globules of air, which 

 passed down the oesophagus 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 oesophagus they usually 

 stop for a short time at the entrance to the stomach, indicating the 

 existence of a valve or sphincter at this place. 



Circulation — The blood of the Caligus, as in most other Articulata, 

 is a limpid fluid, containing suspended in it numerous minute colour- 

 less particles. These particles are very various in their form and size; 

 the smallest scarcely equal ^'^ of an inch. We have observed one 

 particle the length of which was about T j^ of an inch, and its breadth 

 I its length ; another had nearly the same length, and a breadth equal 

 to I its length. These particles can accommodate 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. 

 In this respect the species are very unlike the Sapphirinse, Calam, 



