208 BULLETIN OP THE UNITED STATES PISH COMMISSION. 
use larvae of insects, and especially small fresli- water shrimps, which, as 
we shall see, form an exceedingly abundant article of food, particularly 
in winter. 
When, in the year 1882, I visited the Gremaz establishment for the 
first time, I was positively astounded at the quantity of Daphnia in the 
basins, forming dense clouds in the water. But that was in the begin- 
ning of October, after a long period of fine and warm weather, during 
which these small crustaceans had had the chance to multiply at an 
enormous rate. I was, therefore, curious to return to the establishment 
to see how matters stood during the bad season. From this point of 
view, no better moment could have been selected for my visit. Without 
being exceptionally severe, the winter in this region has been somewhat 
prolonged. Shortly before my arrival the thermometer had fallen to 13 
degrees below zero. On the day of my visit it was still 3 degrees below 
zero, and the basins, which had a feeble current of water, were covered 
with ice. The ice had been broken in several places, and we could, 
consequently, examine the water underneath. I must say that the 
Daphnice appeared to me to be just as numerous as during the fine sea- 
son, which, however, is easily explained in water as cold as that in 
these basins; but when we dipped out some of the water from the bot- 
tom of the basins, with a sort of canvas purse-net, we brought up in- 
credible quantities of larvse of the Chironoma and still more larvae of 
the Ephemera. The whole bottom of the basins seemed to be one mass 
of animal life. At every haul we got a big dish full of these larvae, 
which are an exceedingly valuable article of food for the young fish. 
The water which is artificially prepared for the Daphnia is, therefore, 
likewise well suited for the development of other small aquatic animals 
which can be utilized as food for young fish. 
But Messrs. Lugrin and du Roveray are not contented with this source 
of food. Alongside of the basins there are small rivulets, artificially 
made, for raising small fresh-water shrimps (Gammarus pulex), which, 
by a method similar to the one employed for the Daphnia , are caused to 
multiply in enormous numbers. In these rivulets, filled with water- 
cresses and other aquatic plants, the little shrimps, which form so im- 
portant a part of the food of the trout, are raised. Every day the daily 
ration allowed to the fish is gathered with nets in a few minutes ; and 
it is a curious spectacle to see this food given to the fish. The young 
trout come from all directions in dense masses. They vigorously attack 
the little shrimps, and do not allow a single one to get to the bottom of 
the water. No matter how large the quantity of shrimps it vanishes in 
a few moments. 
The young fish of Messrs. Lugrin and du Roveray thrive admirably 
on this diet. Three basins, each having a surface of about 120 meters, 
contained about 70,000 fish of this year’s raising, grouped according to 
size, and all in excellent condition. From their well developed stomach 
and their finely-rounded forms, it will be seen that these young fish have 
