432 BULLETIN OF THE BUREAU OF FISHERIES. 



what stages this one-sided process can advance before disintegration reaches the point 

 at which the organized life of the individual animal must come to an end. 



The numerous investigations of the U. S. Bureau of Fisheries into the natural 

 history of the salmon — especially the migration, feeding, and spawning habits — have 

 firmly established the facts upon which the general statements made above are based. 

 Of the numerous workers we may especially mention the recent investigations of 

 Mr. Cloudsley Rutter. late naturalist of the Bureau's steamer Albatross, who was 

 one of the best informed men on all scientific questions that pertain to the Pacific 

 salmon. It is to his energy and skilled insight that we are indebted for the more 

 accurate details of the conditions under which the young make the journey from the 

 headwaters of the rivers to the sea, also for details as to the progress of the adults to 

 the spawning grounds, as well as for saving improvements in the methods of propa- 

 gation. Mr. Rutter was at the time of his death in the midst of an exhaustive study 

 of the embryology of the salmon. 



In the solution of the problem of the changes that occur in the salmon during 

 the run to the spawning beds, there are three general courses open, in addition to 

 the natural-history methods of observation. One is a study of the anatomy, by which 

 may be followed the structural changes in the salmon after it reenters the rivers. 

 Little has been done with this method except upon the alimentary canal. A second 

 course is through the methods of physiological chemistry. These have been applied 

 particularly by Miescher-Ruesch in Germany, and Paton and his coworkers in Scotland. 

 The latter especially have published some instructive and interesting studies of the 

 chemical changes in the tissues and organs of the Atlantic salmon (Salmo salar). No 

 work has been published presenting the results of a chemical study of the salmon of 

 our west coast, though the opportunities for observation are far more numerous and 

 the natural setting of the problem is infinitely superior to that for the study of the 

 Atlantic salmon either on the continent of Europe or in Scotland. The European 

 species of salmon which spawns in the rivers of Scotland (Salmo solar), like our 

 American steelhead (Salmo gairdneri), for example, returns to the sea for another 

 period of feeding, thus spawning more than one season. Oncorhynchus tschawytscha, 

 unlike the species of Salmo, does not return to the sea, but spawns once and dies, as 

 was first conclusively proved by the investigations carried on by Doctor Evermann in 

 Idaho in 1895 and 1896/' It therefore presents a peculiarly favorable opportunity 

 for the chemical study of starvation. 



The third and last line of observation seeks to trace the changes in the functional 

 activity of the salmon by the methods of experimental physiology. These methods 

 have never been applied to the study of this species — have been applied, indeed, in 

 only a limited number of studies on fishes of any kind. The present investigation 

 had its origin in the belief that good and fruitful results would be yielded by such an 

 experimental study. Under the auspices of the V. S. Bureau of Fisheries, field 

 work was begun during the summer of 1901. Only a small portion of the total 

 results of the physiological investigations in progress will be reported in the 

 following pages. 



« Bull. U. S. Fish Comm. for 1896, pp. 151-202, and 1S97, pp. 15-84. 



