VII.-INTERNAL PARASITES OF THE FUR SEAL.* 



By Ch. Wardbll Stiles, Ph. D., 



Zoologist of the Bureau of Animal Industry, 



and 



Albert Hassall, M. E. C. V. S., 

 Inspector in the Bureau of Animal Industry. 



SUMMARY. 



I. — Introduction: The first parasitic worms recorded from Bering Sea were 

 collected by Steller in 1742 from the now extinct sea cow (p. 100). Since that time 

 parasites (p. 100) have been mentioned from the far seal of Bering Sea by Elliot, 

 1882, and by the British Commissioners in the Paris hearing, but the worms were not 

 studied. The subject of the parasites of the fur seal bears an intimate relation to 

 the parasites of marine mammals in general (p. 101), but references to the parasitic 

 diseases of marine mammals are meager, and none of them treat the subject in detail 

 (p. 101-102). 



The parasitic worms collected by Lucas in Bering Sea came from the fur seal, the 

 hair seal, and the sea lion (p. 102), and belong to three different families of worms 

 (p. 103) : mawworms of the genus Ascaris, strongyles of the genus Uncinaria, and 

 tapeworms of the genus Bothriocephalus. Of these the ascarides and strongyles 

 are the most important in connection with the subject at hand, and of mawwoi-ms 

 alone we have sufllcient material for proper study. 



II. — Family Ascaridae (p. 103). Qenns Ascaris : Synonymy (p. 103); diagnosis 

 (p. 103). These worms occur normally in the digestive tract, but are occasionally found 

 in other parts of the body (p. 104) ; a few specimens have little or no effect upon the 

 host, but heavy infections may injure the hosts in various ways; by stoppage of the 

 bowels, by wandering, taking food intended for host, wounding the mucosa, production 

 of a toxic substance (p. 104). Noae of these effects have been observed in any degree 

 of importance in the case of the fur seal, but there is no reason to assume that the 

 effects of ascarides upon these animals will be different from the effects of mawworms 

 upon other animals (p. 104). In our opinion, while the mawworms will undoubtedly 

 be a factor in the general debility of seals in cases of excessive infections, the relation 

 of the worms to the mortality of seals will be insignificant (p*. 104). The seals become 

 infected with their ascarides by eating fish; these worms accordingly play no rdle 



' This report on the parasitic worms of the fur seal, collected hy the United States Commission of 

 1896 was prepared under the direction of Dr. D. E. Salmon, Chief of the Bureau of Animal Industry, 

 United States Department of Agriculture, at the request of the Secretary of the Treasury. 



