BRANCHIAL1S. 143 



appendages; neck narrow, of moderate length, and 

 somewhat flexuose ; genital segment usually tolerably 

 elongated, somewhat swollen and tapering slightly to 

 the bluntly-pointed distal extremity; also abruptly 

 folded upon itself in the form of the letter S. Egg- 

 strings long, slender, and twisted into roundish 

 masses under the posterior portion of the genital 

 segment. 



Cephalothoracic appendages rudimentary or obso- 

 lete, except the first pair of maxillipeds, which are 

 situated near the apex of the head immediately behind 

 the mouth ; the four pairs of thoracic legs situated at 

 the proximal end of the neck, and being exactly as they 

 exist in the cyclops stage, both in size and structure. 

 The first and second pairs biramose and both rami 

 biarticulate, but the inner ramus wanting in the third 

 and fourth pairs while the outer is composed of two 

 joints. The whole animal when stretched out, and 

 exclusive of the cephalic horns and the egg-strings, 

 measuring about 40 mm., but the size varies to some 

 extent. Colour dark red, due to the contained 

 blood. 



Cephalic horns usually fixed in the gill-arches of 

 the fish, the tissue of which they simply penetrate 

 when the animal settles on the host, and then become 

 branched, thus securing a firm anchorage. The 

 branches in this species assume a more or less dicho- 

 tomous arrangement, and in this respect differ from 

 the other species to be described. 



Male. The male is very small, and resembles the 

 young female in general appearance. Having reached 

 the cyclopoid stage it undergoes no further change, and 

 is then sexually mature. 



Habitat. The female in the adult fixed stage is 

 usually parasitic on the gills of various Gadoids, as cod- 

 fishes, haddocks, and whitings, and is not uncommon ; 

 while young females with males attached to them may 

 be found on the gill- filaments of flat-fishes such as the 

 flounder, Pleuronectes flesus. The following are some 



