336 . SPINE-FINNED GROUP. 



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 vomerine 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 branchio- 

 stegal 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 5 lbs. 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 indiscrimin- 

 ately 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, 

 upwards of two hundred and eighty thousand having been taken from a fish of 

 | lb. in weight. Fossil remains of the genus occur in the Miocene rocks of (Eningen, 

 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. 334, 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 3 or 4 feet, and attains a weight of from 25 to 30 lbs. 

 Its extreme voracity and destructiveness to other fish render it an undesirable 

 inhabitant of preserved waters. 



Danubian The two small and rather elongated perches represented in the 



Perches. upper part of the illustration on p. 337, the larger of which is 

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

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

 by the body being cylindrical or somewhat depressed; while from two allied 

 genera they are distinguished by the maxilla or main upper jawbone, being covered 

 by the preorbital bone, and by the premaxilla being free only at the side. The 

 body is elongate and nearly cylindrical in form ; and" the mouth situated on the 

 lower surface of the thick and somewhat projecting muzzle. All the teeth of the 



