THE HISTORY OF FISH-CULTURE. 499 



of wood or metal ; but if metal, they must be the samfe as tlie tissue, ia 

 order to avoid galvanic currents, which might hurt the spawn. This 

 apparatus is convenient, for it dispenses with the necessity of changing 

 the water containing the milt. After the fecundation, it runs out of 

 itself through the holes of the sieve. 



The "dry i^rocess"' of fecundating spawn, invented by Mr. Yrasski, 

 differs from the preceding by requiring two vessels, one for the spawn, 

 which is put there without water, and the other for the milt, to which 

 water is added to moisten the eggs. This method is extremely advan- 

 tageous, for in using it scarcely 1 per cent, of the eggs escapes fecun- 

 dation, while in the "moist method" 10 to 12 per cent, of the spawn may 

 be lost. A little spoonful of milt is sufficient to fecundate 1,000 egg.«. 

 What has prevented the spreading of this method, in other countries is 

 the very improbable opinion that it is not applicable to tish which spawn 

 in autumn or in winter, or at a low temperature in general. The 

 l)rincipal conditions of success in the operations which we have just 



j described are always : full maturity of the eggs and milt, a suitable 



j temperature, and rapid execution. 



The following is the method employed for fecundating glutinous eggs : 

 It requires some bunches of aquatic plants, which are carefully washed, 



I {Ranunculus^ Glyceria aquatica, &c.^) a vessel of the shape and size of 

 those used for the preceding operations, and a bucket. The manipula- 

 tions require three persons. One of them holds the female fish, and 

 extracts the spawn from it as described above, while the other extracts 

 the milt from the male. The third person stirs the water with a bunch 

 of plants, to favor the absorption. The spawn sticks to the plants, 

 which are left for two or three minutes in the water containing the 

 spermatozoids, so as to insure the fecundation of the eggs. Then the 

 bunch of plants is washed with the spawn sticking to it, and put in the 

 incubating apparatus. As the fecundation of glutinous spawn requires 

 the aid of several persons, and as, besides, the species of fish which 

 have this spawn do not cost very much, it is usually multiplied in arti- 

 ficial incubating-apparatus, which has the advantage of avoiding almost 

 entirely the loss of spawn, which, in the natural course of events, is 

 inevitable. The construction of this apparatus varies very much. The 

 simplest consists of two pieces of wood joined by several transverse 

 pieces trimmed with aquatic plants. This apparatus is put in the water 

 several weeks before the spawning-season; then it is taken out of the 

 water. The plants are also taken out and placed with the eggs that are 

 on them in the incubating-apparatus. 



5. — THE INCUBATION OF SPAWN. 



After the fecundated spawn has by itself become detached from the 

 fecundating-boxes, it is put in an apparatus with compartments, where 

 the incubation takes i)lace. For this operation we may use a shovel, 

 or we can also simply incline the vase which contains the spawn as near 



