476 EEPORT OP COMMISSIONER OF FISH AND FISHERIES. 



the experiments wbicli he describes, and took great paius to insure the 

 success of them. He perceived that the eggs are easily spoiled when 

 they get into heaps, and recommends, to avoid this danger, the separ- 

 ating them frequently by means of a switch. Care should be taken 

 also that they do not stick together when the milt is poured over them. 

 Finally, the dirt which the water deposits should, from time to time, be 

 carefully removed from them, and this may be readily done with the 

 feather of a quill. 



The question now is, whether Jacobi, by neglecting no precautions, 

 and guarding himself ngainst the various chances of failure, did arrive 

 at a final result which is comi^letely satisfactory in a practical point of 

 view. Did he succeed by means of his process in advantageously 

 restocking water-courses which had become unproductive,^ or increasing 

 production, to any extent, in those where tish were already abundant ? 

 We have not the requisite documents for answering this question posi- 

 tively; but we can scarcely doubt that he obtained at least partial 

 results, since England recompensed his services with a pension, and in 

 a little state of Germany his operations have been continued with suc- 

 cess by M. Schmittger.* 



Physiology soon turned to account the discovery of Jacobi, and arti- 

 ficial fecundations have since been frequently reproduced in laborato- 

 ries. There is no need of recalling the results which Spallanzani, Pre- 

 vost of Geneva, and Dumas have drawn from theui. They have been 

 also a great help to embryological studies; and by emidoying tliis means 

 two contemporaneous zoologists, Rusconi and C. Vogt, have been able 

 to follow all the i^hases of development of the tench and the palie ; but 

 this discovery especially marked a great progress in pisciculture, and, 

 w^hile science availed itself skillfully of this new mode of investigation, 

 the practical results obtained by Jacobi were carried out in Germany 

 and Scotland. 



In the " Treatise on the Economy of Ponds," (by Ernst Friedrich Hartig, 

 p. 411, 1831,) there is given a description of the process of Jacobi, with 

 the remark that this method has been successCully employed by the 

 forester, Franke, at Steinburg, in the principality of Lippe-Schaumburg, 

 as well as by M. De Kaas at Biickeburg. The same facts are confirmed 

 by M. Knoche,t who asserts that he has himself also completely suc- 

 ceeded upon the estate called Oelbergeu. The last writer placed the 

 young tish at first in a little reservoir, and the following year trans- 

 ported them into a larger basin. "I have obtained by this process," says 

 he, " in the eight years that I have been employed, 800 young fishes 

 out of 1,000 to 1,200 eggs. After a year I found in the smaller pond 

 only about half the fish, the others having either died or escaped. 



* This fact is proved by a letter of Dr. Schutt, of Frankfort, recently written to Mr. 

 Milne-Edwards. The experiments of M. Schmittger have been made in the principal- 

 ity of Lippe-Detmold. 



t Journal of the Agricultural Union of the Grand Duchy of Hesse, No. 37, p. 407, 1840. 



