100 21tirfi/-st'n'nt]i Aninuil MeciiiKj 



streams and lakes as well as in the adult salmon niay owe its in- 

 troduction into fresh water to the migrating fish for it would he 

 difficult to conceive that its presence in the adult salmon dated 

 from the time at Avhich the young fish were feeding in fresh wa- 

 ter l:)efore they went out to sea. In any event this instance is 

 unique. The introduction of the j^arasite is unquestionably of 

 long standing and it may l^e possible to ex]ilain the case on en- 

 tirely different grounds. 



It is evident then that the vast majority of parasites which 

 the migratory salmon brings into fresh water streams and lakes 

 in Alaska can find no further possibilities of existence. They 

 perish without completing their life cycles or effectively ])ropa- 

 gating their kind. This large number of individuals wdiich are 

 thus of no avail in tlie ]>erpetuation of the species forms a part 

 of the reproductive surphis which is ])roininently discernable in 

 all parasitic organisms. At the same time the removal of these 

 parasites from the range of the growing salmon tends to re- 

 duce the degree of parasitic infection and to keep this host with 

 the relatively low percentage of ])arasites which characterizes it 

 in comjiavison witli otli<'r marine fisli. 



J.ITEUATrUK CITED. 



Fritsch, A. — 189-1:. Der Elbelachs, eine Ihologisch-anatom- 

 ische Studie. Prag. 



Linton, E. 1899. Parasites of Fishes of the Woods Hole 

 Region. Bull. I'nited States Fish Commission. 



Mcintosh. \V. V. — 1863. Xotes on the Food and Parasites 

 of the Sainio salai'. dour. Linn. Soc, London, Zool. 7. 



Zschokke, Fr. 1899. Erster Beitrag zur Parasitenfauna 

 von Trutta salar. A'erli. naturf. Ges. Basel, 8. 1891. Die Para- 

 sitenfauna von Trutta salar. Centr. Bakt. u. Par., 10. 1902. 

 ^larine Schnuirotzer in Siisswasserfische. \'erh. naturf. ({es. 

 Basel, l(i:l 18-157. 1 pi. 



DISCUSSIOX. 



Dr. Barton W. Evermann : I would like to ask Prof. Ward 

 one question : Whether his studies of the parasites of tlu' Pacific 

 coast salmon show that those ])arasites are of fresh water rela- 

 tionshi])s or salt water relationships, and if the anwer to that 



