HATCHING THE EGGS. 1 29 



These should be sufficient to arrest it effectively. If 

 they cannot be made sufficient, then the stream is not 

 worth using.* 



If by any accident sediment should get upon the 

 eggs occasionally, the method of removing it is so 

 simple, that it need cause no alarm, if it is attended to 

 at once. This method consists merely in watering the 

 eggs with a common garden watering-pot, at the same 

 time keeping the outlet screen clear, to let off the sed- 

 iment as it floats down. This plan, though so simple, 

 is very effective. It will remove every particle of sed- 

 iment from the eggs, and leave them, as well as the 

 bed of the hatching-troughs, cleaner than before the 

 sediment was observed. The agitation also seems to 

 do the eggs good in other ways, f 



I should water the eggs occasionally, even if there 

 were no sediment to be removed. The precaution 



* When the hatching water has so much sediment in it that 

 filtering cannot make it safe for the eggs in the common hatch- 

 ing troughs, the water can still be used sometimes with grilles, 

 by washing off daily with the watering-pot the sediment which 

 collects on the eggs. The sediment will fall through the 

 openings between the grilles, and be out of the way of the 

 eggs. The eggs can be safely hatched in this way, but the 

 sediment must be closely watched and carefully kept off the 

 eggs. 



t " Une autre condition necessaire au developpement des ceufs, 

 c'est de les remuer souvent ; un repos absolu les tuerait neces- 

 sairement." — VSgt, Embryologie des Salmones, p. 16. 



It should be said, in explanation of the above note, that Vogt's 

 experiments were not conducted in running water. This does 

 not, however, invalidate his testimony as to the effect of agi- 

 tating the eggs. 



