568 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



quently known this fisli to reach the weight of thirty pounds in German 

 lakes and ponds. In Germany, carp are often confounded with hybrids 

 of Cyprinus carassius, (Cyprinus Icollarii, Heckel,) or of Cyprinus ahramis. 

 Their quality, however, is much inferior to that of the genuine carp. 



In middle Europe, carp deposit their eggs in the first summer-days — 

 from the beginning of May to the end of Juue. In the south, the fish 

 attains a larger size; that is, it grows faster in the same time, siuce, in 

 northern countries, it is naturally forced into a longer winter-rest. In 

 spring- water it does not thrive at all, requiring warm water in summer- 

 time, with mud at the bottom, and for nourishment, the lower forms of 

 life, (microscopic animal organisms, worms, snails, remnants of plants, 

 &c.) 



The eggs are deposited upon water-plants — not those nearest to the 

 surface and exi^osed to the direct hot sun, but such stems of these icatcr- 

 plants as are about one inch below, to which the eggs, when extruded, 

 adhere. Those falling off" either perish in the mud or are destroyed 

 by numerous enemies. This i>eculiarity of adhesion in the eggs, and the 

 usual position of the stems which serve as their depository, suggested 

 the arrangement of my apparatus. This very simple contrivance con- 

 sists of a number of light, wooden, rectangular frames, about three feet 

 long and one broad, covered on one side with thin gauze or mosquito-net- 

 ting, (PI. XVIII, fig. 3.) Upon these screens the impregnated eggs are 

 spread and immediately adhere. After impregnation, (for which direc- 

 tions are given below,) the frames are placed in a floating box, (PI. 

 XVIII, fig. 1,) the sides of which are covered with some kind of can- 

 vas, but somewhat more open than that of the frames, in order to allow 

 a more rapid change of the water, while i^reventing the escape of the 

 young fish. 



The bottom and cover of this box are made of canvas, each box hav- 

 ing room for three frames ; each frame having on its two sides 20,000 

 eggs, so that the whole box contains G0,000 eggs. The stuff for covering 

 the frames, «S:c., must be soaked for some days in river-water, and the 

 size and coloring-matter carefully removed by washing; no soap, how- 

 ever, should be used. 



THE IMPREGNATION. 



It is, of course, necessary that the fish selected for impregnation 

 should be in a fit condition ; the eggs and milt being neither unripe nor 

 overripe, since overripe eggs do not receive the zoosi)erms well, and 

 overripe milt proves inactive even upon good eggs, its vitality being 

 nearly lost from partial decomposition. If the eggs and milt are im- 

 mature, so as to require considerable force to express them, no success 

 can be expected. It is always advisable to keep ripe fishes confined in 

 running water for several days previous to the impregnation of the egg. 



For the operation itself two persons are required : one, the operator 



