COLORATION OF THE BLACK BASS. 151 



intensity of the red colors of their flesh depends upon the 

 quantity of GammaridcB which they have devoured. 



A striking instance of the difference in coloring of the 

 flesli from the influence of age or season, is related by the 

 well-known European ichthyologist, Dr. Fric, in regard 

 to the salmon of Bohemia. He says that there are three 

 different ascents of the salmon during the year: The first 

 ascent begins in February or March under the ice, and 

 lasts till May. These salmon weigh from twenty-five to 

 fiftv j)ounds, and are famous under the name of " Violet- 

 salmon." The second ascent begins in June and lasts till 

 August. These fish have a reddish flesh, and weigh from 

 twelve to twenty-two pounds, and are known as "Rose- 

 salmon." The third ascent is from September until De- 

 cember. These fish are mostly weak, weighing from three 

 to fifteen pounds. Their flesh is pale, and they are usually 

 called " Silver-salmon." 



The trout of the mountain lakes of the Alps (Salmo 

 salvelinus), according to the season and the nature of the 

 Avater they inhabit, have their flesh whitish or reddish. 



The color a7id condition of the water has likewise a very 

 marked effect upon the external appearance of the Sahnon- 

 idce. Agassiz found that the color of brook trout of 

 neighboring streams was influenced by the color and 

 quantity of the water, and that even trout of the same 

 stream differed in color as they frequented the shady or 

 sunny side. He also found that fish in clear, sunny waters, 

 with gravelly bottoms, were highly and brightly colored; 

 while those in shady streams, or where the bottom was 

 dark or muddy, and the water not so clear, were corre- 

 spondingly dusky in hue; and that bright fish taken from 

 waters of the former character and placed in those of the 



