292 LAKE SUPERIOR. 



c 



PERCA GRANULATA Cuv. et Veil. Hisfc. N. Poiss. 1828, II., 48, PL 9. 



Jard. Nat. Libr., I., 92, PL \.-Dekay N. Y. Fauna. 1842., 



p. 5, PL 48, f. 220. Linsl. Cat. Fish. Conn. 

 PERCA SERRATOGRANULATA Cuv. et Val. H. N. Poiss. 1828, II., 



tf. G-riff. in Cuv. An. K. X., PL 39, f. \.-Dekay N. Y. 



Fauna. 1842, p. 5, PL 22, f. 64. 

 PERCA GRACILIS Cuv. et Val. H. N. Poiss. 1828, II., 50. Richards. 



Fn. Bor. Amer. 1836, III., . Dzkay N. Y. Fauna, 1842. p. 6. 



Closely resembling the European species, the yellow perch of 

 America differs however considerably from it, so that no naturalist 

 after Cuvier, who first distinguished them from each other, has ever 

 thought to identify them. Its several varieties, described first under 

 particular names, seemed then to constitute species quite as distinct 

 from each other as the Perca flavescens is from the Perca fluvi- 

 atilis. But at that epoch, when the principle of the constancy or per- 

 manence of species had just been placed upon an anatomical foun- 

 dation, naturalists for a time lost sight of this other fact, that the 

 species common to a fauna are subject to individual variations which 

 run over the whole range of the species. To study these changes, 

 to bring back every variation to its true type, to trace the circle of 

 the species through so many oscillations, was a task whose results 

 could not be anticipated. The principle of the permanence of 

 species has remained in our science as a well-ascertained fact, but 

 naturalists have found that many which had been distinguished 

 as species had to be cancelled as soon as their characters were better 

 understood. Thus, in a series of more than forty individuals of 

 the yellow perch of America, we can no longer trace the limits of 

 separation between the Perca granulata, serrato granulata, acuta 

 and gracilis, which all belong as mere varieties to the P. flavescens, 

 as Dr. Storer has already determined. A more pointed snout, a 

 more slender form, a more wrinkled head, more marked wrinkles 

 on the operculum, and the denticulation of the opercular bones, 

 are not constant characters, any more than the color, or the number 

 of the transverse bands, which vary with the age of the individual. 

 We have examined perches from the Sault St. Mary, from Fort 



