GREAT BRITAIN. 37 



such as are kept in more natural conditions. Some breed- 

 ing fish, as the conger, seem to be unable to extrude their 

 eggs when in an aquarium, and, so far as I have observed, 

 die in the vain attempt to discharge them, possibly owing 

 to want of some particular form of pressure which they 

 obtain when in a wild state. That pressure may be neces- 

 sary, I would advert to M. Carbonnier's observations how 

 the male of the curiously grotesque telescope-fish, a variety 

 of the gold carp, acts as accoucheur. Three males pursued 

 one female, which was heavy with spawn, and rolled her 

 like a ball upon the ground for the distance of several 

 metres, and continued this process, without rest and 

 relaxation, for two days, until the exhausted female, who 

 had been unable to recover her equilibrium for a moment, 

 had at last evacuated all her ova. 



Respecting the artificial propagation of the eggs of 

 marine fishes, except in America, but little has been at- 

 tempted. It was found that a certain amount of motion 

 was necessary in order to cause the eggs of the shad to 

 develop, so a box was invented, having a wire gauze 

 bottom, in which they were placed. These boxes were 

 secured at an angle to floats, so that a current passing 

 through kept the eggs in constant motion. The success 

 was found to be great. Since then the hatching of cod 

 and other marine fish eggs has been extensively carried 

 out. 



There are certain conditions of the water more or less 

 suitable for the residence of fish, and among these tem- 

 perature plays an important part, more especially in the 

 sea, where it everywhere determines the distribution of 

 animal life. It may act directly upon the fish through the 

 water, or else upon the food upon which it subsists. It 

 may delay or accelerate breeding, or even injure the eggs, 



