2704 THE BONY FISHES AND GANOIDS 



The common perch (Perca fluviatilis), which is a fish of wide 

 distribution, and one too familiar to require detailed description, is 

 the type of a small genus, agreeing with eight others in the following characteristics: 

 In the head the mucus or slime canals are but moderately or slightly developed on 

 the top and at the sides; and the spinous and soft portions of the dorsal fin are 

 separate. In common with six other genera, the body is more or less compressed; 

 the perches and pike perches being specially distinguished by having usually seven 

 (rarely eight) gill rays; by the premaxillse or anterior upper jawbones being 

 capable of protrusion, and by the serration of the preopercular bone of the gill 

 cover. As a genus, the true perches are distinguished from the pike perches by 

 the small and uniform size of the marginal teeth, and the close approximation of 

 the pelvic fins. There are teeth on the palatine and vormerine bones, but none on 

 the tongue, and there are thirteen or fourteen spines in the first dorsal fin, and two 

 in the anal. The scales are small, the upper surface of the head is naked, the 

 preorbital as well as the preopercular bone is serrated, and there are seven branchi- 

 ostegal rays and more than twenty-four vertebrae. As in most of the members of 

 the family the mouth is capable of a certain degree of protrusion. The common 

 perch, which seldom exceeds five pounds in weight, is distributed over the rivers of 

 Europe (except Spain) and Northern Asia as far east as Lake Baikal; two others 

 being known, namely, P. flavescens from the Eastern United States and P. schrenki 

 from Turkestan. Generally preferring still waters, and occasionally descending 

 into estuaries, the perch is one of the most voracious of fishes, feeding indis- 

 criminately upon worms, insects, and small fishes. The spawning season in 

 England is at the end of April or May, when the female deposits her eggs in net- 

 shaped or elongated bands on the leaves of aquatic plants. The eggs are very 

 numerous, upward of two hundred and eighty thousand having been taken from a 

 fish of one-half pound in weight. Fossil remains of the genus occur in the Miocene 

 rocks of CEningen, in Baden, and those of the extinct Paraperca in the upper 

 Eocene of Provence. 



The pike perches, of which the common European representative 

 (Lucioperca sandra) is shown in the upper figure of the illustration on 

 p. 2702, are inhabitants of many of the lakes and rivers of Europe, Western Asia, 

 and Eastern North America, and take their name from their somewhat elongated 

 and pike-like form. From the true perches they differ by the presence of more or 

 less enlarged tusks in the marginal series of teeth, and by the wider interval 

 between the pelvic fins. The two dorsal fins are rather low, the first having from 

 twelve to fourteen spines, and the scales are small. The common species, which 

 is confined to Eastern Europe, where it is much esteemed as a food fish, grows to a 

 length of three or four feet, and attains a weight of from twenty-five to thirty 

 pounds. Its extreme voracity and destructiveness to other fish render it an undesir- 

 able inhabitant of preserved waters. 



The two small and rather elongated perches represented in the 

 Perche upper part of the illustration on p. 2705, the larger of which is known 

 as Aspro zingel and the smaller as A. vulgaris, may be taken as rep- 

 resentatives of a subgroup distinguished from the foregoing forms and their allies 



