140 THE CANADIAN NATURALIST. [April, 



After the lapse of about four weeks, it will be well to take the 

 hatching-boxes out of the case to ascertain which eggs are good. 

 The action of the air will render them all transparent ; but on re- 

 placing them in the water, the unfruitful ones will assume a 

 milky opaque color. These can readily be removed with a pair of 

 fine pincers or long tweezers. The exposure to the air does not 

 hurt the eggs, but care must be taken that they do not become 

 dry on the surface. After repeating this process three or four 

 times, all the bad eggs can be removed. " I am convinced," is 

 the remark of Professor Rasch, •' that in a case of the above size 

 I could hatch 10,000 salmon-ova in each box, which would thus 

 give a total of 160,000," there being four hatching-boxes in each 

 of the four compartments. If the fry are to be kept any time in 

 the boxes, care must be taken that they be not overstocked ; but 

 3,000 may well be kept in them from two to three months." 



Where water from a spring cannot be directly obtained, the fol- 

 lowing plan is often adopted. The scale of operations is however 

 necessarily more limited. A large tub, or other wooden vessel, is 

 fitted with a tap. Care must be taken that it shall have previously 

 lain a sufficiently long time in water, so that all the deleterious 

 substances from the wood shall have been extracted. It is then 

 placed on a stand at a sufficient height from the ground to allow 

 the case containing the hatching-boxes to be placed beneath the 

 tap ; and they should have a gentle inclination, so that the upper 

 end be about half an inch higher than the lower. 



The water, having passed through the boxes, empties itself into 

 another vessel, at least as large as the tub, and should be regulated 

 that it shall run out in twenty-four hours. The tub, therefore, 

 only requires replenishing once in that time. If the water be at 

 all muddy, it is well to place a layer of fine sand mixed with char- 

 coal at the bottom of the tub. 



Even in a common tea-saucer a great many ova may be hatched 

 out. The saucer is placed in a deep soup-plate, and a couple of moss- 

 stalks laid over the edge in such a manner that they shall act as 

 syphons. A constant flow of water thus takes place from the sau- 

 cer into the plate. In about twelve hours half the water from the 

 saucer will have run out, so that it will require filling again morn- 

 ing and evening. When necessary, fresh moss-stalks can be sub- 

 stituted. 



It is of course best to procure the male and female fish to be 



