260 Description of a Species of Caligus. - 



ment, the cuiTent comes from the buccal cavity and carries the 

 whole below. 



The irregularity in the circulation in this animal is even greater 

 than will be inferred from the above description. These currents 

 are merely main directions ; the blood flows into them or from 

 them, through all their extent. The current coming laterally 

 down to the base of the second pair of natatories, besides going 

 into the natatory and on the back, is carried up the venter at each 

 of the upward vibrations of the ventral current. The current 

 from the apron also passes into the same current, in addition to its 

 backward course. When it is considered that the currents of blood 

 occupy merely the spaces left by the muscles and other internal or- 

 gans, it will be readily seen that similar irregularities must occur in 

 various parts of the body. These directions are occasionally sub- 

 ject to singular deviations. One of the two currents which run 

 from each side in front, and unite on the medial line, has been ob- 

 served to cross the medial line into the other current, and thus 

 continue flowing for some time with considerable force ; soon af- 

 ter, each flowed by vibrations towards the centre, but with alter- 

 nate motion. This was observed immediately on taking the Cali- 

 gus from the water, when it was apparently very lively. As the 

 cod, however, had been for several days confined in the harbor 

 near the market, all the specimens examined may have lost part 

 of the activity usual in the open sea. At times, the blood in some 

 parts merely vibrates back and forward, without advancing in 

 either direction ; and occasionally the blood flows in a direction 

 exactly the contrary to its usual course. 



We have not fully satisfied ourselves of the mode of respira- 

 tion in the Caligus. The natatory pinnulse — to which we must 

 add those of the tail, as they are identical in their structure — have 

 been supposed to supply the place of branchise. When the ani- 

 mal is attached to any object, these legs keep up a very regular 

 action, which appears to correspond to the palpitations in the 

 body.* We have not, however, observed the blood to flow into 

 their setae, and the currents passing into the legs are among the 

 least regular. We are disposed to believe that these pinnulse are 

 not the special organs for this function, but that aeration takes 



* This action is not so rapid and branchial-like as in the Argulus, but takes 

 place at intervals of about one and a half seconds. 



