INTERNAL PARASITES OF THE SEBAGO SALMON. II 87 



associated. The head, which was not contracted, showed on careful study the 

 deUcate outHne of a rudimentary end organ. While such a structure was not 

 demonstrated in the mature individuals described above, one can say positively 

 that if present it could not have been seen owing to the greatly contracted 

 condition of the adult scolices. I believe that its presence will be demonstrated 

 in more favorable specimens. The complete agreement of this largest larva 

 with the mature specimens in all other features compels me to regard both as 

 different stages in the development of the same species. 



The other larvae were still in early stages of development, and probably 

 had been ingested by the salmon at a very recent date. Their relationship is 

 not so clear in all respects, and yet I do not hesitate to associate with the new 

 species of Proteocephalus a plerocercoid or young cestode obtained from the 

 same host as the adult worms and the older larva just described. The head is 

 broadly conical, without furrows, and measures 0.3 mm. in breadth. The 

 suckers measure 60 to 7511 in diameter. There is no rostellum or fifth sucker 

 to be found, while the end organ is so poorly developed as to be visible with 

 difficulty and only under the most favorable circumstances. The neck is 

 nearly as broad as the head. In general appearance this larva resembles the 

 adult cestode and the older larva previously described. With some reserve one 

 may also assign to this species a single plerocercus taken from another specimen 

 of Salmo sebago. The head, which measures only 150M in breadth, is shaped 

 like that of the young cestode and like it is without rostellum or fifth sucker, 

 while the end organ is difficult to demonstrate. Neither furrows nor ridges are 

 seen on the larva, which has a total length of 1.14 mm. The sucker measures 

 onlv 30 to 45^ in diameter. The neck is slightly narrower than the head. 

 This form certainly belongs to the genus Proteocephalus and probably to the 

 species already described. 



From the scantiness of the material obtained one might infer that the 

 Sebago salmon is only a casual host of the species. Yet I did not secure this 

 parasite from any other fish in Lake Sebago and adjacent waters, and I have 

 not met it in fish examined in other places. The presence of larvae in different 

 stages of development with only a few adult specimens in any one host, 

 although some were found in the majority of the salmon examined, would 

 rather favor the view that the cestode was a regular though infrequent parasite 

 of this host. 



Sparganum sebago, nov. spec— In addition to the cestodes already men- 

 tioned, there are to be noted two specimens of bothriocephalid larvae which 

 deserve more extended mention. 



The first was taken from the spleen of one salmon. It measured 25 mm. 

 in length and 1.8 mm. in maximum diameter. There is no neck, but the body 



