THE HISTORY OF FISH-CULTURE. 475 



of fish, tlie trout and the salmon. He tells us himself that, before arriv- 

 iug- at good results, he had to employ sixteen years in preparatory 

 researches and incomplete experiments. He remarked, in the first place? 

 that from the end of November to the beginning of February the trout 

 come together in the brooks and fix themselves upon the gravel, wliere 

 the^' rub their bellies in a way which leaves large tracks. The females 

 then deposit their eggs, upon which the males drop their milt. He 

 caused some trout, tlien, to be taken at this season, when ready to spawn ; 

 taking by turns a female and a male, he pressed their abdomen liglitly 

 over a vase half filled with water, and let fall into it the mature products 

 of both sexes, and then stirred up the whole with his hand, in order to 

 render the mixture more complete, and thus to insure the fecundation 

 of all the eggs. These eggs being once fecundated, it was necessary to 

 combine the circumstances proper for their development, and for this 

 purpose Jacobi thought of placing them in a grated box, across a little 

 brook of running water. He constructed a large chest, at one extremity 

 of which, and on the upper surface, he left a square opening, barred by 

 a metallic grating of which the threads were separated by a space of 

 only about four lines ; this opening served to let in the water. Another, 

 grated in like manner, and placed in the vertical face of the other ex- 

 tremity, allowed it to flow out. The bottom was overlaid with an inch 

 of sand or gravel. Jacobi placed this apparatus in a trench prepared 

 for it by the side of a brook, or, better still, a pond fed by good springs, 

 from which he could cause, by a canal, an nninterupted stream of water 

 to flow through the box. 



These dispositions, very simple and judiciously combined, completely 

 resolved the problem which he had proposed to himself, viz : To pro- 

 tect the fecundated eggs against their natural enemies and yet to leave 

 them in circumstances similar to those in which they Aivonld naturally 

 have been placed. The experiment succeeded. After about three 

 weeks, Jacobi saw appearing through the thick envelope of the egg 

 two black points corresponding to the eyes of the animal, and eight 

 days later he began to distinguish the body itself, which moved and 

 turned in the interior. Finally, after five weeks, the young fishes broke 

 from their shells, and soon separated themselves completely from it, 

 retaining only, under their bellies, a hanging yellow pouch, which is 

 the umbilical vesicle. During nearly a month the young were nour- 

 ished by the substance of this pouch, which disappears as they increase 

 in size; but then they had need of other nourishment, and to obtain it 

 they left the box by passing through the grating, and fell into a reser- 

 voir filled with sand and fitted to receive them. Jacobi adds that, in a 

 basin of sufficient size, they grew wonderfully in the space of six months, 

 and that then they had arrived at a suitable growth for stocking the 

 ponds; but he does not say in what way he nourished them during all 

 this time. 



The inventor of artificial fecundation appears to have often repeated 



