228 



LOWER VERTEBRATES. 



northern temperate zone, and about eighty species are known. So far as size is con- 

 cerned, there are two groups ; one contains comparatively large species, of which 

 there are only three in America and about ten in Europe and Asia; the other is rep- 

 resented by about seventy species exhibiting some remarkable variations, and is 

 restricted to North America. 



The common perches of Europe and America are very closely related, and consti- 

 tute the genus Perca, which, by successive restrictions, has been reduced from an 

 immense and unnatural assemblage to three species. The perches are moderately 

 elongate and compressed fishes, with thirteen to fifteen spines in the first dorsal, 

 which is entirely distinct from the second, the head without enlai-ged raucous cavities, 

 and the teeth small. The common European perch is the P- flumatilis ; the Ameri- 

 can, P. americana. 



The American yellow perch is an inhabitant of many of the streams and ponds of 

 the eastern United States, especially to the northward. In appearance as well as 



Fig. 128. — Perca amerUana, yellow perch. 



habits, it is very like the European fish, but is held in much less esteem, both as a food 

 and game fish, in America than in Europe. 



The largest and best of the PercidfB are the pike-perches, comprised in the genus 

 Stizostedion or Lucioperca. The body is more elongate and less compressed than in 

 the yellow perches, the spines of the dorsal more numerous (17 to 23), the head 

 broader but also without mucous cavities, and some of the teeth are much enlarged 

 and canine-like. Pike-perch is rather a book than vernacular name, and the most com- 

 mon one is pike, qualified by some prefix, such as wall-eyed, yellow, blue, or gray. 

 They are, however, neither like the true pike nor related to it, but on the contrary 

 they are closely related to the true perches. 



Wall-eyed pike, yellow-pike, blue-pike, salmon, jack-salmon, glass-eye, and dory are 

 names in which the largest of the American pike-perches (*^. vitreum) rejoices, in 

 some one or other section of the United States. It is dark olive with indistinct 

 oblique brassy lines ; the first dorsal has a large black blotch behind, and the pectorals 

 ai-e dusky and plain, or without blotches. It attains a weight of ten to thirty pounds, 

 and a length of nearly three feet. This species, which for brevity we call glass-eye, 

 is one of the most important food-fishes of the lake region, and in some places ranks 



