ARTIFICIAL PROPAGATION OF THE RAINBOW TROUT. 247 
it is a, good idea to run a feather tlirougli tlie eggs for the purpose ot changing t'neir 
liosition on the trays and to disclose any dead eggs or foreign matter that may he 
hidden underneath. Great care should be exercised in handling the eggs at any time, 
but after the first or second day from the taking until the appearance of the eye-spot, 
they should be handled with especial care, and then only when it is absolutely neces- 
sary, as during this period they are very delicate, and a good shaking up, or even 
l)assing a feather through them, will cause a heavy loss. 
Fig. 3. — Interior view of Hatchery showing men fishing ont Dead Eggs. 
Time required to hatch the eggs . — The time re(piired to hatch trout eggs, or fish 
eggs of any kind, depends almost wholly upon the temperature of the water in which 
they are placed. I do not know of any rule that can be depended upon in all cases. 
In ‘‘Trout Culture,” by IMr. Seth Green (page 29), I find the following regarding the 
incubation of eggs of tlie brook trout: 
A rule suflicieutiy accurate for all practical purposes is this: At 50 degrees the eggs will hatch in 
50 days; each degree colder takes 5 days longer, and each degree, warmer 5 days less; the difterenee, 
however, increasing as the temperature falls and diminishing as it rises. 
The above rule is as good as any that I know of, but it will not do to depend upon 
it in all cases. The rainbows, however, will hatch out from 2 to 5 days earlier in any 
case than the brook trout. 
Hatching the eggs . — Two trays of 12,500 eggs each are as many as should be left in 
one trougli for hatching; with this number in a trough — using my horizontal sliding 
screen in the upper end — there is but little danger of the alevins congregating 
