SALMON AND TROUT TN ALASKA, 



89 



to the difference in time at which the different schools arrive at the 

 breeding stream. 



Variations in counts. — For a further test of the similarity of fishes 

 from a given basin, counts were made of the dorsal and anal fin rays, 

 the branchiostegal rays, and of the tubes of the lateral line and 

 number of longitudinal rows of scales. These various counts are tabu- 

 lated in the same manner as the measurements, except that sexes 

 are not differentiated, percentages being used instead of the number 

 of examples in order to make comparable the results for the different 

 sized lots that were obtained. In the fui-ray counts the totals of 

 rudimentary and branched rays are used, but the terminal half ray, 

 which varies greatl}' in development, is in all cases omitted. 



In table 6, showing the counts for dorsal rays, the similarity of 

 the two years for each of the various localities is striking; Yes Bay, 

 Karta, and Quadra exhibit the maximum on 15 rays, while Dolomi 

 and the two Moira Sound points give it to the next lower number, 

 or 14 rays; 12 and 17 are the extremes. The averages differ very 

 slightly; Karta Bay is highest with 14.7 and Nowiskay lowest with 

 14.3. It is noteworthy that these two localities were examined in 

 sequence in 1904, and the field notes call attention to the exact identity 

 of method in recording the fin counts. 



Table 6. — Dorsal Fin-Ray Count. 



In the anals (table 7) the parallel is less sharply defined but stiU 

 characteristic. All reach the maximum on 18 except Dolomi and 

 Nowiskay in 1904, which rise highest on 17. The extremes are 15 

 and 20. Quadra shows the lowest percentage on 17 and highest on 

 19. The averages vary from 18.2 at Quadra to 17.3 at Nowiskay. 

 The order of localities as to number of rays is changed from that of 

 the dorsals, though the Moira Sound streams are still lowest. 



