18 U. S. BUREAU OF FISHERIES 
upon the trays and the surplus water removed by squeezing a bunch 
of it between the hands. 
When packed, the trays of eggs are placed upon a tray filled with 
moss, the upper tray of eggs also being covered with a tray of moss. 
The entire stack is then covered with an ice hopper, preferably of 
galvanized iron and with small drainage holes along the outer edge 
of bottom. Best results will be had if a block of ice, rather than 
chopped ice, is fitted into the ice hopper. 
PLANTING THE FRY 
In order to prevent loss from the fry preying upon each other, 
whenever practicable they should be planted before the sac is fully 
absorbed, but not for three or four days after hatching, since if they 
are so held they, gain strength, and if they are to be transported 
some distance they become better fitted to withstand the hardships 
of a long journey. But with large numbers, running into hundreds 
of millions, lack of space makes it necessary to liberate them almost 
as fast as hatched. Darkening the tanks prevents cannibalism, but, 
owing to the absence of food and possibly to the darkness, the fry 
become weak and light colored in a day or two and will not stand 
transportation. They must, therefore, be transported before the 
sac 1s fully absorbed or large numbers will be lost by either canni- 
balism or starvation. 
During the season of 1899 the water pumped from the lake for 
the supply of the fry tanks at the Put in Bay station hterally teemed 
with Crustacea, such as Cyclops, Diaptomus, Daphnia, Alonopsis, 
etc., but at first, after the food sac was absorbed, the fry refused 
to partake of these, their supposed natural food, and preyed on each 
other instead. Three or four days later, however, a few hundred 
fry held for experimental purposes devoured these Crustacea greed- 
ily and throve upon them as long as the supply lasted. When can- 
nibalism was at its height 50 fry were placed in a tin pan with 
myriads of Crustacea. In 10 minutes there were six cases of canni- 
balism. In each case one of the fry seized the tail of another and 
swallowed all it could. Close watching failed to discover any of 
these fry attempting to seize one of the Crustacea. It was also 
discovered that neither the fry of the whitefish nor of the pike perch, 
when later they began to feed on the Crustacea, would touch a 
Diaptomus, although the most showy of all the Entomostraca 
present and resembling very strongly the Cyclops, with which it is 
closely related. When a hungry fry would, as if by accident, seize 
a Diaptomus it would at once reject it and go about showing un- 
mistakable signs of discomfort. Contrary to the general belief, the 
fry do not always die from the effects of eating other fry. The 
swallowed portion may be digested and the head and attached tis- 
sues finally rejected. 
It has been customary to employ the same method in planting 
pike-perch fry as in planting whitefish fry; that is, the fry are 
dipped from the fry tanks of the hatching battery into cans or kegs 
and transported on a steamer to the points selected, where the cans 
are lowered into the water and the young fish allowed to swim out. 
Se 
