FLESH PARASITES OF MARINE FOOD FISHES. 



I20I 



When we turn to the intermediate hosts of these cestodes we find no such 

 hmitations. For example, there is a cestode {Tetrarhynchus bisnlcaius) which is 

 of common occurrence in the dusky shark in the Woods Hole region. I found 

 the same or a closely related species in a shark, which was rather doubtfully 

 identified as a blue shark, at Beaufort, and two specimens, not yet mature, in 

 a sharp-nosed shark (Scoliodon terras-novce) at that place. This cestode may 

 be said to be practically limited to the dusky shark as its final host. I have 

 found it encysted in at least i8 species of fish at Woods Hole, in 22 at Beau- 

 fort, and in 2 in Bermuda. The intermediate hosts of this parasite include a 

 great range of species. They are not even confiined to the teleosts, but include 

 some of the sharks and skates as well. The occurrence of encysted cestodes in 

 sharks and skates is not as rare as it was thought to be by Beneden, who 

 coined the word xenosite, or stranger, for such cases. 



It does not come within the plan of this paper to give details of distribu- 

 tion. The following typical examples, therefore, will probably be sufficient to 

 illustrate this matter of the limitation in the number of final hosts and the wide 

 range of intermediate hosts. 



Distribution of Typical Cbstodes in Final and Intermediate Hosts. 



In view of the frequency of occurrence of cestode parasites in body cavities of 

 marine fishes their comparative rarity as flesh parasites is striking. While 

 larval cestodes have been found in the great majority of the species of fish I have 

 examined, in those cases where a considerable number of individuals were 

 examined the number of species of fish in which I have found parasites in the 

 flesh is surprisingly small. A glance at the appended tables will show the small 

 number of fishes found to harbor parasites in the flesh among those examined in 

 the summer of 1908. WTien it is remembered that with no more than three 

 exceptions entozoan parasites have been collected from all the species of 

 fish named in the tables, that flesh parasites are recorded from only 12 species 

 out of a total of 76, and that in only 2 of the 12 species were flesh parasites found 

 in many individual fish or in large numbers in any, the comparative scarcity of 

 flesh parasites in the marine fishes becomes a still more noteworthy fact. 



