9IO BULLETIN OF THE BUREAU OF FISHERIES. 



of this current which determines and creates the dangers to which the eggs 

 and the fry are exposed — this, first, because the quantity of water suppHed to 

 the apparatus is not sufficient; second, because all obstacles, as the partitions 

 in the apparatus, operating to prevent a current, become a hearth of infection 

 of all kinds, by the corners they make; third, because of the very dimensions 

 and the shape of these troughs; and fourth, the visible proof, because there 

 are found in these troughs and in the rearing troughs fry large enough to be 

 able to maintain an equilibrium, yet lying on their sides, with gills compressed 

 against the bottom of the basin and in contact with the slimy ooze of the bottom. 

 If the fish makes a movement, it is only to fall back on the other side, so that 

 the gills are by turn infected with noxious substances from the bottom, which 

 can not be seen and cleaned as it ought to be. 



The greatest cleanliness is always necessary in fish culture, and it must be 

 made attainable. Let us see, without being pessimistic, what the conditions 

 most often are. 



The fish-cultural apparatus found on the market has not all been invented 

 by fish culturists having a knowledge of this science. The manufacturer sells 

 apparatus the advantages of which he extols with the aid of so-called fish- 

 cultural tracts (though in reality they are not such), and the inexperienced 

 purchaser establishes his business immediately, with confidence of success. 



If he buys eyed eggs, he will not have the same difficulties as the man who 

 collects the eggs himself. Let us take the latter for example. The eggs are 

 placed on the grilles and the grilles in the troughs, all these things being more 

 or less well washed, but the wooden screens can not be put in the flame so as to 

 destroy all germs. Then there may be among the eggs excretions of fishes 

 that may have fallen in the stripping, or there may be shells of broken eggs, 

 all of which may drop through the grille to the bottom of the trough, to be left 

 there during the entire period of incubation, together with any dead eggs that 

 may have slipped between the glass bars. 



If the water contains sediment, this will be deposited on the bottom of 

 the trough and will remain there. The fish culturist has been told that all he 

 has to do is to take out the few dead eggs and await the hatching of the 

 others before cleaning out his apparatus. Water is not the same everywhere; 

 all has its advantages and its disadvantages; in France the incubation takes 

 place in water the temperature of which varies during this period from 

 6° to 12° C. (I do not refer to the mountain region), and often the incubation 

 period lasts from forty-five to fifty days. It is well known that some eight 

 days before the first hatching some eggs will burst. Theu" contents, escaping, 

 spread over the eggs in long filaments which attach themselves to the grill, 

 pass through it, go to the bottom, increase the amount of sediment, and 

 encourage the invasion of Saprolegnia. 



