118 



THE FUR SEALS OP THE PRIBILOF ISLANDS. 



characteristic lips were then visible. A small, conical spiue, about 20 /( long, is also 

 present on the tip of the tail; this spine is finely striated tranversely and is curved 

 ventrally or dorsally. Of internal organs, the intestinal tract is well developed; the 

 oesophagus is divided into an anterior portion about 1.8""" long and a posterior 

 portion about 0.8'"'" long; in younger specimens (fig. 20) in which the oral tooth was 

 present, the oesophageal and intestinal caeca were absent, but in sitecimens which 

 had shed the oral tooth the intestinal caecum was present, the intestine and rectum 

 were distinct. From lack of time the other internal organs were not studied carefully. 

 Yon Linstow (1878, pp. 237, 238) described a young nematode from the muscles 

 of Osmerus eperlanus under the name Ascaris eperlani. These worms measure 23.4""" 

 long by 0.72""" broad; the oral tooth is absent, but the three lips are present; the 

 intestinal caecum is also present. '■^ Nematoideum salmonis eperlani Bud." is given 



Kg. 19. 



as a synonym, and Agamonema bicolor Diesing is mentioned as the embryonic form. 

 This latter worm von Linstow also found in Osmerus eperlanus; it measured 8.8'""' 

 long by 0,23""" broad, the oral tooth was present, and the intestinal caecum was well 

 developed. Later von Linstow (1895, pp. 519-524) describes Ascaris eperlani more in 

 detail and suggests that it represents the larval stage oi Ascaris decipiens. Agamo- 

 nema bicolor was first described as Filaria bicolor Creplin, and is reported from " Perca 

 fluviatilis, Acerina vulgaris, Osmerus eperlanus, Lota communis, and Gasterosteus 

 fluviatilis." 



Von Linstow may be correct in his supposition that the worms known as Agamo- 

 nema bicolor [Filaria bicolor), Nematoideum salmonis eperlani and Ascaris eperlani 

 represent the younger stages of A. decipiens, in which case the five fish just mentioned 

 would form intermediate hosts, but our experience with the earlier determinations 



