CHEAP FIXTURES FOR THE HATCHING OF SALMON. 9G3 



black a good deal of rough handling can be practiced without the slight- 

 est harm, and they can be safely shaken about upon the tray until 

 thoroughly washed. A pair of tweezers will be needed to pick out the 

 white eggs, and I would recommend a home-made article, shown in Figure 

 13, consisting of two pieces of wood tacked together and tipped with 



Fig. 13. 



wire loops. They are much easier to the hand and altogether better than 

 metallic tweezers. In water of 46° F. the dead eggs should be removed 

 daily; at 45°, every two days will answer; at 40°, every three days; at 

 33°, once a week ; but these are maximum periods and should never be 

 overstepped. 



If the eggs are neglected, the first result is that the dead ones begin to 

 decay and taint the water, rendering- it unfit for the healthy eggs. In 

 the next place, if left long enough in the water, the decaying egg is at- 

 tacked by a fungoid growth, of which the technical name is Achlya pro- 

 lifera. This is what is commonly termed "fungus," though some writers 

 have applied the term "fungus" to a totally different plant, a kind of 

 Conferva or slime, which is either colorless or green, grows in long fine 

 threads, and where too much light is admitted to the trough multiplies often 

 to such an extent as to prove a nuisance, but never is troublesome in a dark- 

 ened trough, and never, so far as known, feeds on animal matter. The 

 Achlya, on the contrary, feeds on animal matter, and, so far as my own 

 observations go, always on dead and decaying animal matter, never attack- 

 ing a living egg. It grows in long white threads which radiate from the 

 object upon which it is feeding, giving it a woolly appearance. It grows 

 rapidly, spreads over all surrounding objects, and may do harm to good 

 eggs by shutting off the circulation of water from them and thus exposing 

 them to the poisonous exudations from the decaying substance. The 

 presence of this growth in a hatching-trough is a sure sign of neglect ; 

 for, if the dead matter is removed before decay sets in, Achlya will never 

 make its appearance. 



The screens and filters must be daily or oftener examined to see that they 

 are not choked up, for a few hours' stoppage of the flow might have disas- 

 trous results. If any emergency arises requiring a stoppage of the water for 

 several hours, before the fish have broken the shell, it can be safely done 

 if, at the same time, the water be drawn off from the trough, for which 

 purpose a movable plug should be put in the bottom of every trough. 

 Eggs are not injured by exposure to the air for however long time, pro- 

 vided they do not fr«eze nor get too warm nor dry up. But after the fish 

 are hatched of course this cannot be done. 



