VARIETIES OF TROUT, 85 



the growth of vegetables : and it is to the 

 leaves of plants, which afford a continual sup- 

 ply of oxygen to the water, that the impreg- 

 nated eggs usually adhere ; so that researches 

 of this kind might be conducted within doors 

 in close vessels, filled with plants exposed to 

 the sun. I have myself kept minnows and 

 sticklebacks alive for many months in the 

 same confined quantity of water, containing 

 a few confervae ; and their ova and melt in- 

 creased in the same manner, as if they had 

 been in their natural situation. 



Orn. — I conclude, from your statements, 

 Halieus, that nothing more is required for the 

 production of fishes from impregnated eggs 

 than a constant supply of water of a certain 

 temperature furnished with air ; and of course 

 the same principles will apply to fishes of the 

 sea. 



Hal. — There can be no doubt of it : and 

 fishes in spawning time always approach great 

 shallows, or shores covered with weeds, that, 

 in the process of their growth, under the 

 influence of the sunshine, constantly supply 

 pure air to the water in contact with them. 

 G 3 



