260 Description of a Species of Caligus. 
ment, the current 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 partsof 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 pinnule—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 sete, and the currents passing into the legs are among the 
least regular. We are disposed to believe that these pinnule 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. one and a half seconds. 
