204 Flow to obtain it. 
things work together. Nature has provided them, and we have 
only to go in and occupy the position that is open to us. A fact 
that has been observed over and over again is, that where Nature 
places the fish there are the necessary food supplies, but only up 
to a certain point. If we wish to go beyond that point we must 
increase the food as well as the fish. 
I have recently been paying special attention to the cultivation 
of perch (ferca fluviatilis ), and on investigating the natural breed- 
ing grounds I found that where the ova were about to hatch there 
were myriads of living creatures, all ready for the little fish to live 
upon when the time arrived for them to require food. Yet we 
hear of individuals condemning perch culture, because when the 
eggs are hatched in pure barren water the little fish all die. There 
is no wonder that they do. The cultivation of the Corregonide 
has been condemned on the same ground. The little fish are 
very small and delicate at first, aud as soon as they lose their sacs 
they die from the same cause. But is that any reason why we 
should abandon the thoughts of their cultivation? All the more 
reason for persevering in it until the difficulty is overcome. 
Having examined some of the waters of the great American 
lakes, in which the Corregonide (white fish) are found in very 
large numbers, I found the lower forms of life exceedingly abun- 
dant. It is on these lower forms that the white fish feed, and the 
very first discovery of this important fact is probably due to Dr. 
P. R. Hoy, of Racine. He also found that certain forms were 
parasitic on the white fish, and it is a noteworthy fact that he 
failed to find any of these in the stomachs of the fish. This 
certainly does not apply, however, to all parasitic organisms. 
There is one very remarkable occurrence, and that is that 
the excreta of fish produces a suitable zdus for the growth of some 
of these minute forms, and, therefore, what is looked upon as a 
nuisance to be got rid of may be made a means of promoting fish 
life. True it is that everything has its use in nature. We find 
that decaying vegetable matter provides some of the conditions 
which foster the growth of these lower invertebrate forms, and we 
have had some remarkable instances of the effect of this on 
newly-made artificial lakes. One thing it is necessary to note, 
however, and that is, that in some cases the organisms partake so 
