INTERNAL PARASITES OF THE SEBAGO SALMON, II57 



Only four of the 129 salmon examined were free from parasites, and in 



all 20 species of the latter were recorded from the infested fish. The list of 



parasites recorded is as follows: 



Ascaris adunca Rudolphi. 

 Ascaris angulata Rudolphi. 

 Ascaris clavata Rudolphi. 

 Ascaris (Agamonema) capsularia Diesing. 

 Ascaris (Agamonema) communis Diesing. 

 Echinorhynchus acus Rudolphi. 

 Echinorhynchus agilis Rudolphi. 

 Echinorhynchus proteus Westrumb. 

 Distomum varicum Zeder. 

 Distomum reflexum Creplin. 

 Distomum miescheri Zschokke. 

 Schistocephalus dimorphus Creplin. 

 Bothriocephalus infundibuliformis Rudolphi. 

 Bothriocephalus osmeri (larva) von Linstow. 

 Bothriocephalus sp. i (larva)." 

 Bothriocephalus sp. 11 (larva). 

 Rhynchobothrium paleaceum (larva) Rudolphi. 

 Tetrarhynchus solidus Drummond. 

 Tetrarhynchus grossus Rudolphi. 



Tetrarhynchus macrobothrius von Siebold ( = vStenobothrium appendicula- 

 tum Diesing). 



Five of these species {Ascaris capsularia, Distomum varicum, Bothriocephalus 

 infundibuliformis, Rhynchobothrium paleaceum, and Tetrarhynchus macrobo- 

 thrius) are abundant, almost regular in their occurrence, while the other forms 

 are relatively rare in the Rhine salmon. The common parasites were also 

 usually abundant in the individual host; thus 20 to 40 specimens of Ascaris 

 capsularia were often found in a single host. Of Distomum varicum, from 30 

 to 50 individuals were taken from the oesophagus of one fish. In some cases 

 Bothriocephalus infundibuliformis was present in large numbers, but usually 

 in one or a few weak, starved specimens. Rhynchobothrium paleaceum and 

 Tetrarhynchus macrobothrius occurred in from 20 to 25 individuals in a single 

 host. All other parasites were found in small numbers, often only a single 

 specimen of any one species. 



Among the 129 Rhine salmon investigated 4 were free from parasites, 55 

 sheltered a single species of parasite, and 43 but two species, while 20 had 

 three species, 6 had four species, and i had five species of parasites. 



o The various bothriocephalid larvs which occur in the salmon are discussed in a separate paper 

 by Zschokke (1890). On the basis of morphologic data he inclined in this paper to the view that five 

 different forms, indicating as many species, might be distinguished. Later studies showed the first to 

 belong to Bothrioceplialus osmeri \ on Linstow. This is the form he listed at first (1889) as Bothrio- 

 cephalus sp. The second is sp. 1 of the table, the third and fourth are united as sp. 11 of the table, 

 and the fifth becomes sp. in of the table (see p. 1168). 



