THE HISTOEY OF FISH-CULTUEE. 497 



3. — SELECTION OF MALE AND FEMALE FISH. 



For artificial fecuudatioii it is indispensable to select fish which have 

 attained their full reproductive maturity, and, as much as possible, at 

 the very time when the spawn is ejected. This condition is very 

 important; for fish, when it is at the natural height of its existence, is 

 only with great difficulty kept in a condition favorable to reproduction. 

 In order to follow the progressive maturation of the spawn of the female 

 fish, so as to be able to use it at the proper time, one proceeds in the 

 followiug manner-; Several male and female fish of one species, or of 

 two species if one wants to cross the breeds, are i)laced in reservoirs 

 large enough to allow the fish to move freely. Every species is placed 

 in a reservoir specially arranged in such a manner as to let each one 

 have the temperature and the kind of water which it prefers. The 

 trout, for instance, the various kinds of salmon, and the sturgeon, which 

 propagate in running cold water, must be preserved in reservoirs fed 

 from sources of fresh water ; and if these cannot be had, the water must 

 be changed frequently. Other species, such as the large pik.e, the carp, 

 the perch, &c., which deposit their spawn in stagnant water, must be 

 placed under similar conditions. In the establishment of Nikolsky the 

 fish are preserved in ponds of running water, and a short time before the 

 fecundation they are transferred to basins likewise supplied with running 

 water, which are in the establishment itself. 



When it is impossible to get living reproductive fish, one may use 

 dead ones. Thus, during the first time of its existence, the establish- 

 ment of Nikolsky had frequently to use, and nearly always with success, 

 dead female fish which came from St. Petersburg. During the trans- 

 portation, the genital aperture was closed with bandages, and the fish, 

 wrapped up in hemp, were laid on their backs. It has been positively 

 proved that the milt, as long as it is contained in the reproductive 

 organs, preserves its prolific qualities for a very long time, and does not 

 even suffer from cold, but if diluted with water it loses its strength very 

 quickly. According to the testimony of several scientists, (Quatrefages,) 

 every movement of the spermatozoids is stopped in milt which is diluted 

 by water, under the most favorable conditions, in the pike in 8 minutes 

 50 seconds, with the roach in 3 minutes 10 seconds, in the carp in 3 

 minutes, and in the perch 2 minutes 40 seconds. As regards the 

 spawn, we have not yet exact data as to how long a time it preserves 

 the faculty of receiving the influence of the spermatozoids according to 

 the temperature and the species. 



^Yhen the eggs and the milt have attained their full maturity, which 

 can be seen by certain external signs, (the swelling of the belly of the 

 female and the enlargement of the genital opening of the male,) one 

 proceeds to fecundate, which is done in two ways, according to the spe- 

 cies of fish. 



S. Mis. 74 32 



