Acanthocephala 



79 



relationship between this particular host and its parasite is ' just 

 as clearly demonstrated in the records from Oneida Lake. Most 

 of the fishes of this species examined were infested with E. thecatus. 

 Though the infestation was quite general the number of individual 

 parasites removed from the digestive tract of a single host was much 

 smaller than has been observed in other localities. From Oneida 

 Lake fifty-four specimens is the greatest number taken from a single 

 specimen of M. dolomieu, while I have frequently taken more than 

 two hundred specimens from a single small-mouthed bass from Lake 

 Pepin, Minnesota. 



One of the most interesting records of the occurrence of E. 

 thecatus is that of its appearance in relatively large numbers in the 

 digestive tract of AnguiUa rostrata. This is the first record of the 

 occurrence of this species in the American eel.* Conditions for 

 infestation must have been especially favorable, because each of the 

 four specimens of eel that carried an acanthocephalan infestation 

 yielded E. thecatus in numbers ranging from nine to forty-nine. The 

 extent of the infestation and the number of parasites from each 

 host is fully as great as that for small-mouthed black bass of the 

 same locality, though the latter has been generally recognized as the 

 normal host of E. thecatus. For this reason it does not seem prob- 

 able that the infestation of AnguiUa rostrata in Oneida Lake could 

 be considered as accidental. 



The writer has discovered E. thecatus in the intestine of the pike- 

 perch from other localities, but this is the first published record of 

 its occurrence in this host. 



The number of specimens of each fish examined was in each 

 instance too small to justify any statements regarding percentages 

 of infestation. Since, however, the available data are of interest 

 in showing the relative extent of infestation, the results of the 

 examinations for this and the following species are arranged in 

 tabular form. 



Table I. 



Analysis of the occurrence of E. thecatus in Oneida Lake hosts 



HOST SPECIES 



AnguiUa rostrata 



Micropterus dolomieu. . 

 Ameiurus nebulosus ** 

 Stizostedion vitreum . . . 

 Amhlopliies rupestris . . 

 Esox reticulatus 



Number 

 infested 



with 

 Acantho- 

 cephala 



Vial numbers 



36, 54, S6, I2S 



73, 75, 77, 182, 183 



IS 



84 



79 



99 



Number 

 infested 

 with E. 

 thecatus 



speci- 

 mens in 

 individual 

 hosts 



9-49 

 1-54 



*Van Cleave, 1920a, published after this report went to press. 



* * Determination doubtful, as careful distinction was not always made between A. natalis 

 and A. nebulosus. 



