98 Thirty-screittlt Annual Meeting 



rials in the stomach except in rare cases when I detected some 

 small objects not necessaril}^ of food character which had appar- 

 ently been swallowed by accident. The alimentary canal becomes 

 highly modified in appearance during the period of migration. 

 At first one tinds considerable quantities of white mucus pres- 

 ent. This l)ecomes much reduced in \olume and changes until 

 only a little more flviid material remains and this is of a green- 

 ish Ime. These changes have no apparent effect upon the })ara- 

 sitic fauna. Those forms which were present at the start were 

 still present at the close of the migration. To be sure in some 

 fish which were examined last or which apparently had been 

 longest in fresh water I discovered a few cestode larvae which 

 seemed to be of recent introduction but this, which may be desig- 

 nated as the fresh water element, was relatively insignificant. 

 The forms were small in size and never more than few in num- 

 bers. 



In one respect the aspect of the salmon changes markedly. 

 After a stay in fresh water it acquires regularly large numbers 

 of a parasitic copepod, wliich line the oral cavity and gills. I 

 have never seen a single specimen of this on a salt water fish. 

 It may l)e regarded as a striking fresh water contribution to the 

 ])arasiti(' fauna of the Alaska salmon. Of course this gill para- 

 site has no relation to alimentation since it is introduced dur- 

 ing the acts of respiration and fastens itself to the mucous mem- 

 l)rane of the mouth and gills as the current of water passes 

 througli. The cestode larvae noted above are the only forms 

 which by any possibility could have any connection with food 

 matter taken in fresh water. Consequently the purely trivial in- 

 crease is strong confirmatory evidence of the fact that the Alas- 

 ka salmon does not feed during its fresh water existence. In 

 this respect then the Alaska salmon manifests an evident biolo- 

 gical similarity to that of the Ehine. In other respects there is 

 manifested a distinct biological contrast. In the Alaska salmon 

 the parasites are reduced little if any in number during migra- 

 tion and the percentage of infection is exceedingly variable in 

 si)ecimens taken under all the varied conditions. Furthermore, 

 one nuiy maintain positively that at the close of the migratory 

 period after a long stay in fresh water the parasitic fauna of the 



