264 Description of a Species of Caligus. 
were discoverable in the interior on that side. Moreover, the 
corresponding ovary near the stomach was discovered with difli- 
culty, and appeared like a folded empty sac. At the same time 
the ovary and the ovarian tube on the other side presented their 
usual appearance. This singular derangement was observed in 
a full grown female, which was perfect in all its other organs. 
An additional peculiarity as yet inexplicable, has been observed 
in some females. The lappets at the extremity of the abdomen, 
each side of the tail, have been already described as very short in 
the female. On their lower surface there is an irregular osseous 
process, from which a slender corneous organ, which we suppose 
to be a duct, runs forward and a little inward, gradually diminish- 
ing, and terminates with a few irregular curves, (fig. 18, Pl. V.) 
The peculiarity we refer to, is an appendage to this lappet, arising 
from the termination of the internal duct, (fig. 22.) It is a long 
corneous duct, wholly external, terminating in an oval sac of similar 
texture, and usually filled with a whitish fluid. These appendages 
have been observed in a few instances, hanging each side of the 
terminal joint of the body, (fig. 22.) In one instance the ducts 
were crossed over the adjacent articulation, and each attached by 
its sac to the lappet of the opposite extremity. _ These are the only 
facts that have been discovered respecting these singular organs. 
They were found attached to very few individuals, and in these 
the eggs were scarcely developed. 
On account of the many similarities between this animal and 
the Argulus, it may be interesting to trace a few of its ana- 
logies. 
The number of legs or organs for locomotion is the same, be- 
ing eight in each. Of the four pairs of natatories in the Argulus, 
two are similar in their use in the Caligus, while a third is expand- 
ed into an apron, and a fourth is attached to a distinct joint, and 
has but little strength. The anterior pair of maxillipeds in t 
Argulus very much resemble in general form the same orgalls in 
the female Caligus. The fourth pair is large and prehensile in 
each, though very different in form. There is a distinet suture 
in the former, near the anterior margin of the animal, which cor- 
responds to the articulation between the two cephalic segments 
in the latter; but this segment, which in the Caligus is furnished 
with antenne, is wholly without even rudiments of these organs ; 
we may hence infer that the Argulus is destitute of antenne, as 16 
