204 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Mr. Lugrin was for many years a practical fisherman on the Lake of 
Geneva. He noted the steady diminution of the more important species 
of fish iu the lake, and sought to ascertain the cause. He gradually 
reached the conclusion that the germ of the trouble lay in the growing 
scarcity of minute Crustacea and the larvae which are the natural food 
of the trout and other fish, especially during their first months of nu- 
trition. 
After elaborate experiments, he hit upon a system by which Daphnia , 
Cyclops , fresh-water shrimps (Oammarus pulex ), etc., could be bred in 
countless myriads at a merely nominal cost. The hatching and rear- 
ing of a generation of these minute creatures is the work of from twelve 
to fifteen days, and as the process may be repeated — or rather repeats 
itself — again and again in the same water, the problem would seem to 
be solved. 
Whoever has watched from a place of concealment the trout feeding 
in an American stream has admired the adroitness with which they 
work down stream, raising with their noses the up-stream edge of flat 
stones until the current, catching underneath, aids the clever little for- 
ager to turn over the stone and expose the minute larvae and Crustacea 
on which he so voraciously feeds. It is the purpose of the process now 
under consideration to raise by artificial means these same species of 
organisms, and in such quantities that the young fry may not only be ! 
abundantly fed in tanks or small inclosed ponds, but ample supplies 
provided for enriching larger streams and ponds where, for some rea- ; 
son, the natural supply may be insufficient. 
The apparatus is simple, and visitors properly introduced have no 
difficulty in seeing the entire establishment at Gremaz, which occupies 
a gently sloping piece of ground, about 6 acres in extent and watered i 
by three springs, which yield collectively about 500 gallons of water per 
minute. The tanks are rectangular excavations, about 120 feet long by 
12 in width, with a depth of 5 feet. The ground being of a gravelly char- 
acter it was necessary to line the walls and bottom of some of the tanks 
with cement in order to retain the water, but in close clayey earth this 
would be needless, and the natural dirt bottom, if not too muddy, would 
be preferable to cement. The tanks have the same general level, and 
are divided by sliding gates of wire gauze sufficiently fine to prevent 
the passage of the fry. Thus far all is simple and obvious. The proc- 
ess of Mr. Lugrin, which has been patented in several countries, con- 
sists in spreading upon the bottom of these tanks a material impreg- 
nated with the elements necessary to produce spontaneously a limitless 
number of Daphnia , Cyclops , Limncea , as well as fresh- water shrimps, and 
the larvse of various Ephemera which form the natural aliment of trout 
and other Salmonidce at all stages of their growth. Once constructed 
and inpregnated with this producing material — which is of trifling 
cost — these tanks go on with their work automatically and indefinitely. 
