384 Scientific Intelligence — Zoology. 



the rearing of these fishes even in localites very remote from those 

 to which salmon naturally resort when they leave the sea for fresh 

 waters. 



In fact, it is not even necessary, for the success of fecundation, 

 that the fishes employed should be alive. M. de Golstein has fecun- 

 dated the ova of a trout which had been four days dead, with entire 

 success. It is probable that the fecundating liquid likewise preserves 

 its properties long after the death of the males. This is, at all events, 

 a fact which I have often verified in regard to invertebrata. More- 

 over, young fishes, after they are hatched, are nourished, for a pretty 

 long period, at the expense of the vitelline substance enclosed in their 

 intestines. Salmon, in particular, appear to have no need of other 

 nutriment till the end of a month or six weeks. It will be seen that, 

 to the other advantages presented by the process of which we speak, 

 we must join that of facilitating the dissemination of species. Our 

 rivers, ponds, and lakes, may easily be enriched with species valuable 

 for the delicacy of their flesh, or for their great fecundity. Attempts 

 have rarely been made to naturalise foreign fishes, and yet the suc- 

 cess of some trials ought to have encouraged experimenters. The 

 Gourami of China has been naturalised in the ponds of the Isle of 

 France, and afterwards in Cayenne. China has furnished us with 

 the gold fishes (Cyprinus auratus) so common in our ponds. The 

 carp itself, now spread throughout Europe, very probably came from 

 Persia. First introduced into the south of Europe, it was not till 

 the middle ages that it penetrated into Prussia, and that country has 

 now made it a considerable article of commerce. It was not, till the 

 sixteenth century that it was imported into England and Denmark ; 

 later still into Sweden and Russia, and although it loses somewhat 

 in size, it bears the rigorous winters of these countries very well. 

 The employment of artificial fecundation, applied and perfected by 

 experience, would certainly one day give an entirely new importance 

 to the management of ponds, and render a produce, which is now ne- 

 cessarily irregular and, at most, triennial, an annual produce. It is 

 well known that a rest of three years, at least, is necessary before a 

 pond that has been fished can be repeopled. This is a great incon- 

 venience ; in order to remedy it, it would be necessary to divide the 

 pond into three or four compartments of unequal size, communicating 

 with each other by means of sluices. The smallest of these com- 

 partments should be arranged for hatching the ova and rearing the 

 fry ; every year the fishes might be driven from one compartment 

 into the other, until they reach the last, which might thus be fished 

 to the bottom every year, and immediately re-stocked by individuals 

 from the next compartment. Reserves placed at the sides would 

 enable us, moreover, to preserve fishes M'hich we wished to become 

 old. — (V Institute Qth November 1848, p. 342.) 



9. On Electric Fishes. — M. R. Wagner has laid before the Aca- 

 demy of Sciences, an extract from his new researches on electric 

 fishes. 



