468 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



of reproduction, the case being applicable to- the males with 

 their sheddinir of the milt as well as to the females. Such 

 mortality is less frequent in the sea, as the fish can, with very- 

 little trouble, and without any artificial impediment, secure 

 that depth of water after the eggs are laid that will meet 

 their requirements.. 



In the same connection, the author reminds us of the fact 

 that nearly all species living at great depths come into shal- 

 low water to spawn, and considers this a proof of his hypoth- 

 esis in regard to the pressure upon the swollen abdomen. 

 He, however, makes no reference to the increasing tempera- 

 ture, as well as greater amount of light secured, both of which 

 have a powerful influence on the development of the egg. 

 Mr. Carbonnier calls attention to the difiiculty which has 

 been experienced in the artificial hatching of the L'Ombre- 

 Chevalier, or /Salmo umbla, a species of trout, and one of the 

 most esteemed of this kind in Europe. This lives in deep, 

 cold lakes, and comes to the shallow water at the proper 

 period to spawn. Numerous attempts have been made to 

 propagate this fish in ordinary ponds, but hitherto without 

 success ; until Mr. Ricot, of Clermont-Ferrand, made his ex- 

 periments in a lake about three hundred feet in depth, repre- 

 senting a pressure of more tlian eight atmospheres. Here 

 the old fish could readily return to the proper depth, and the 

 young follow them at a suitable time. 



An important point mentioned by the writer is in reference 

 to the relation between depth and temperature. He remarks 

 that in the waters of France the trout will not survive a 

 temperature of over 60 at the surface ; but if the water is 

 deep enough to permit them to descend to a depth of ten to 

 fourteen feet, they can readily sustain the heat of 62 to 65; 

 this, as he supposes, in consequence of the fact that the 

 greater pressure neutralizes the expansion consequent upon 

 the temperature. It is on the considerations just presented 

 that he finds an explanation of the alleged fact that it is very 

 difficult to keep fish alive in cans or vessels of limited mag- 

 nitude immediately after the period of reproduction ; such 

 species as the carp and tench, which, under ordinary circum- 

 stances, can be kept in good condition for several hours, even 

 in damp grass, dying in a vessel of water in a very short 

 time immediately after spawning. 10 B, January^ 1873, 16. 



