61 
and impregnated with this producing material—which is. 
of trifling cost—these tanks go on with their work auto- 
matically and indefinitely. The water from two to three 
feet in depth, being left undisturbed two or three weeks, 
is found peopled with swarming myriads of minute 
organisms of the species above named. Twenty thous- 
and trout a year old, or three thousand two years old— 
which last should average about one-half pound in 
weight—are considered sufficient for a pasture of that 
size, and the avidity with which they rush to occupy 
and ravage their new feeding-ground is a delight to the 
pisciculturist. If the propagation has been ordinarily, 
abundant these 20,000 young fry or 3,000 yearlings will 
subsist royally in a tank of the size indicated for an entire 
month, They will eat on an average 20 to 25 pounds of 
food per day, or 600 to 800 pounds per month. Careful 
experiment has demonstrated that each tank at Gremaz 
will produce 650 to 900 pounds of Crevettes (fresh-water 
shrimps), to say nothing of the myriads of Daphnia, Cyc- 
lops, and other species produced in the same water at the 
same time. When, at the close of the month, the tank 
has become depleted, the gate is opened and the fish 
driven like a flock of sheep to new and similar pasture. 
The first tank, being closed and left in quiet, immediately 
begins the process of reproduction, and at the end of two 
or three weeks is swarming again with the varied minute 
organic life which far surpasses in value, as food for fish, 
anything that has been yet devised by man. Thus the 
simple, inexpensive process goes on from year to year, 
the fish always heaithy and vigorous and larger at two 
years old than those artificially fed are at the age of three 
years. Yearlings bred in this way are strong and capable 
of making their way in any open stream or pond sup- 
plied with food and suitable for their existence. One 
thousand of such yearlings have been found more effec- 
tive in stocking a depleted trout stream than fifty thou 
sand young fry turned in, as has been so often done 
