some having essentially a single mode. Water 

 temperature records were examined in connec- 

 tion with times of migration, and there appears 

 to be a relation between the two. Of the fish in 

 the lake, however, only those of a certain race 

 will segregate and respond to the stream tem- 

 peratures of its own stream . These races 

 might, then, be geographical races, ecological 

 races, or temperature races . 



Differences in mean total length of fish in 

 spawning runs have been measured, and sig 

 nificant differences found between streams The 

 differences may be due to differences either in 

 age composition or in growth rate, but in either 

 case they would be racial differences, since 

 sizes of fish in different streams bear the same 

 relationship to each other year after year . Size 

 differences have also been compared for fish 

 caught in two areas of the lake, and have been 

 found to be significantly different . 



Ball, O. P. 



1955. 



Cope, 0. 

 1953. 



Evermann, 

 1893. 



LITERATURE CITED 



Some aspects of homing in the 

 cutthroat trout. Proc. Utah Acad. 

 Sci., Arts, and Lett., Vol. 32, 

 pp. 75-80. 



Length measurements of Lake Yel- 

 lowstone trout. U.S. Fish and 

 Wildlife Service, Special Scientific 

 Report- -Fisheries No. 103, pp. 1-17. 



B. W. 

 A reconnaissance of the streams 

 and lakes of western Montana and 

 northwestern Wyoming. Bull. 

 U. S. Fish Comm. for 1891. 

 Vol. XI, pp. 1-61, plates I-XXV, 

 2 maps . 



Sizes of eggs and numbers of eggs per Mayr, E., 



female from eight streams were compared in 1953. 



relation to sizes of fish. Counts and measure- 

 ments did not always correspond to the figures 

 that would be expected if the fish were all of the 

 same race. Some streams had small fish with Miller, R. 



relatively large eggs, suggesting that some 1950 . 



races diverged from the general relationships 

 to be expected. Difference in numbers of eggs 

 per unit of ovary weight were measured among 

 three streams . 



Acknowledgment is made of the data on 

 egg numbers and ovary weight collected by Dr. Simpson, G. 



Stillman Wright, of the records on hatchery egg 1939. 



take provided by Mr. William EXinn, Superin- 

 tendent of the Yellowstone hatchery, and of the 

 fish counts and measurements secured by many 

 fish culturists and biologists of the U.S. Fish 

 and Wildlife Service. Mr. Martin Laakso, 

 Fishery Research Biologist at Logan, very kindly 

 aided in checking computations . 



E. G Linsley, anckRL. Usinger. 

 Methods and principles of systematic 

 zoology. McGraw-Hill,- New Yorki 

 i-ix, 1-328. 



R. 



Notes on the cutthroat and rainbow 

 trouts with the description of a new 

 species from the Gila River, New 

 Mexico. Occ . Pap. Mus. Zool . 

 Univ. Mich., No 529, pp. 1-42, 

 1 map, 1 plate . 



G. , and A. Roe 



Quantitative zoology. McGraw- 

 Hill, New York, i-xvii, 1-414. 



84 



