264 Descriptmi of a Species of Caligus. 



were discoverable in the interior on that side. Moreover, the 

 corresponding ovary near the stomach was discovered with diffi- 

 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 the 

 Argulus very much resemble in general form the same organs in 

 the female Caligus. The fourth pair is large and prehensile in 

 each, though very different in form. There is a distinct 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 antennse, is wholly without even rudiments of these organs ; 

 we may hence infer that the Argulus is destitute of antennas, as is 



