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[21] PROPAGATION OF WHITEFISH AT NORTHVILLE, MICH. 573 
cially destructive to the live eggs at this time, it being the most critical 
period in the life of the egg, so far as the influence of confervaceous 
growth is concerned. During the period just mentioned, and with a 
temperature of water ranging from 40° to 45°, ten dead eggs scattered 
equidistant on a 7 by 12 tray, containing 10,000 live eggs (in water) will 
soon accomplish the destruction of the remainder, if allowed to remain 
undisturbed. Eggs thus neglected are doomed. 
From the thirty-fifth to the forty-fifth day the eyes of the embryo be- 
come plainly visible, and the egg from this time on may remain in con- 
tact with fuagous growths much Icnger than previously without injury. 
From this time on, too, the work of caring for the eggs continually 
lessens. 
THE HATCHING JARS. 
With reference to bringing forward eggs of the whitefish in hatching 
boxes and applicable more particularly to the earlier stages of develop- 
ment, it may truthfully be said that “eternal vigilance” is the price of 
success. But this statement cannot be made concerning the develop- 
ment of embryos in the Chase hatching jar; for, while incubating in this 
manner, the eggs are not subjected to critical periods, and thus the 
necessity of a constant surveillance at certain times is obviated. Hap- 
pily, too, the introduction of the jar does away with the primitive one- 
by-one-picking process with nippers, unavoidably a slow and tedious 
operation requiring the persistent patience of a Chinaman. The jar, 
then, greatly lessens and simplifies the work, thereby reducing the 
expense to a nominal figure. Safety and economy constitute its chief 
points of superiority over any hatching device in which the eggs are 
stationary, or,at best, have but very little movement; more economical, 
because one man having but little experience or instruction can readily 
care for 20,000,000 eggs; and safer because the dead eggs are separated 
by the natural operation of the jar as soon as confervoid growth begins. 
Previous to this growth, however, separation of the dead from the liv- 
ing eggs by any mechanical arrangement of currents or counter currents 
would seem to be impossible as there is no apparent difference in their 
specific gravity; but the spongy filaments of morbid growth, without 
materially increasing the weight of eggs thus affected, present a greater 
surface to the influence of the current which, having an upward tend- 
ency, carries and retains them either against the gate or just above 
the surface of the mass of eggs whence they are easily syphoned away. 
Unless great care, demanding considerable time, is observed, and which 
is not at all essential, the syphon will draw away many good eggs, and 
frequently good eggs will be found with the bad ones at the gate; but 
when all such are transferred to a separate jar, a solid layer of varying 
depth of the worst eggs will soon rise to the surface and can then be 
drawn away without disturbing the remainder. 
During the early part of the season, the eggs collecting at the wire 
gate and those hovering over the mass of.eggs were removed twice daily 
