1864.] ON PISCICULTURE. 129 



diflfer from the great authorities who use the glass bars : for in the 

 first place, the fish do not find glass bars at the bottom of the water 

 on which to deposit their eggs, but they always find gravel; in 

 the second, it is absolutely necessary that the egg should be per- 

 fectly motionless for some thirty-five or forty days. If you place 

 a round egg against two glass bars which are also round, the whole 

 being under water, you at once get the best possible conditions for 

 motion of the egg on the glass bar at the slightest touch, and you 

 certainly do not get what you chiefly want, — perfect immobility ; 

 for if the water be turned on from a tap a little too fast, or you 

 happen to touch one egg with a camel-hair brush, all the eggs in 

 the box immediately run against each other, and begin to dance 

 and roll about. Again, when the young fish begin to hatch out, 

 their umbilical bags very often get caught between the bars, and 

 then they perish ; or if they fall through, they get into water that 

 is much too deep for them, and whence it is very difficult to 

 extract them without disturbing every egg in the box. This is 

 done in the French plan, by taking out a cork and letting the 

 water run off from under the bars. 



By placing the eggs on gravel, on the contrary, all this diffi- 

 culty is obviated. The eggs can be placed so that they do not 

 touch one another ; so that the dead ones do not contaminate their 

 live neighbors, and may be easily picked out by a pair of forceps ; 

 so that the inequalities of the gravel will keep them perfectly 

 steady ; so that the young fish when coming out of the egg 

 — like the young snake casting his skin in a furze-bush — may have 

 facilities afi"orded him to get rid of his shell, and be not like his 

 neighbor on glass bars, who slips about thereon like a clumsy 

 skater upon well-swept ice. 



You will observe, of course, when you examine the fish-hatchino* 

 boxes now in the room, that we do not in one respect adhere to 

 nature ; that is, we do not cover the eggs with gravel, as does the 

 parent fish. The only reason why the parent fish buries her eggs 

 is because of the light, which is unfavorable. All roots and seeds 

 of plants, we may observe, are buried in the ground ; it would ap- 

 pear, therefore, that at first darkness is absolutely necessary for the 

 development of the first germs of life. Again, if the eggs are 

 exposed to the light, a white fungus immediately appears 

 upon them. All this is obviated in a moment by placing wooden 

 covers on the boxes, for these keep out all the light, and obviate 

 Vol. I. I No. 2. 



