IXYERTEBRATE ANIMALS OF YIA^EYAED SOUND, ETC. 457 



tain species have been found in Crustacea, otliers in mollusks, &c. Mr. 

 A. Agassiz has briefly described, but not named, a remarkable worm 

 that he found very common in the jelly-fish, Mnemiopsis Leidyi, and the 

 young of this or a different species was observed by me in the same Aca- 

 leph. It appeared to be a species of Scolex. It was pale purple, with 

 light 3'ellowish orauge stripes. I have i^reviously mentioned a round 

 worm {Ascarisf) which frequently occurs in winter in one of our species 

 of Sagitta. 



Most of the species that, in the adult state, inhabit fishes, live while 

 young, or in the larval stages, in smaller fishes, or in other animals, 

 upon which the larger fishes feed, and from which they thus derive their 

 parasites. 



Besides the parasitic worms there are also many internal parasites that 

 belong to the Protozoa. 



The external parasites of fishes are also numerous. They are chiefly 

 Crustacea and leeches. 



Among the Crustacea there are a few species of Amphipods that are 

 parasitic. One of these, Lapliystms sturioniSj lives upon the gills of 

 fishes and upon the surface of the body. It was found on the gills of 

 the " goose-fish," {Loplihis^) in Vineyard Sound, and on the back of 

 skates at Eastport. It is remarkable in having large claws developed 

 on the third and fourth pairs of legs, those of the first and second be- 

 iug small. Its color is light red. 



Certain Isopod Crustacea, belonging to the genus Livoneca (Plate Yl 

 fig. 29) and allied genera, live in the mouths and on the gills of fishes, 

 clinging firmly to the membrane of the roof of the mouth, or other 

 parts, by means of their strong sharp claws. These are generally 

 unsymmetrical inform. The species of the genus Bopyrus live on the 

 gills, under the carapax of shrimp and other Crustacea, x)roducing large 

 tumors. A species is common on species of Rippolyte in the Bay of 

 Fundy ; and a species has been found in this region. The genus Cepon 

 is allied to the last, and our species occurs under the carapax of the 

 " fiddler-crabs " in this region. 



Among the Entomostraca the number of parasitic species is still 

 greater, but most of these live on the external surface and gills of fishes, 

 though some of them occur also in thp mouth. The species of Panda- 

 riis and allied genera adhere firmly to the skin, and are provided with a 

 proboscis. They are very common on sharks, but occur also on other 

 fishes. A laiHlari( t e YII, fig. 31) Rud Nogagus LatreilUi {Finite 

 YII, fig. 32) were both f )uud on " Atwood's shark," the " man-eater" of 

 this region, associated also with Nogagus tenax. The species of ^^Noga- 

 gns^^ are merely the males of other genera, for no one has yet deter- 

 mined both njales and females ot the various species. The young of 

 one species, CaUgiis rapax, were found swimming free at the surface. 



The species of Argulus and allied genera are less strictly parasitic, or 

 rather they adhere less closely, and apparently leave the fishes at pleas- 



