63 
young without the intervention of the male; these 
young are all females and all likewise capable of repro- 
ducing without the male. The mother gives birth to 
living young every three or four days, say an average 
of 15 to a litter. Ina week or ten days these young 
are mature and begin in their turn to reproduce. Thus 
in the course of 60 days, according to one calculator, 
the descendants of a single Daphnia may number more 
than twelve hundred millions. Such enormous fecundity 
is not found, | think, among any other creatures that 
are of suitable size to serve as food for fish. The other 
entomostraca are also very prolific. 
Given plenty of entomostraca, the first condition of 
growth of young fish is met. But the multiplication 
and growth of the entomostraca is only possible when 
they too have an abundance of food, and they also are 
animal feeders. So another group of animals still more 
minute must precede the entomostraca. These are 
found among the protozoa, whose food is decaying 
vegetable and animal matter, such as is found to a 
certain extent in ordinary rich earth, and much more 
abundantly in animal excrement and the debris of 
succulent plants. Thus the basis of the system is a 
pond-bottom rich in animal and vegetable matter in 
process of decay. This nourishes abundance of pro- 
tozoa ; the protozoa nourish the crustacea ; the crustacea 
nourish the fishes. 
The question naturally suggests itself how far we may 
expect a system devised for carp and found applicable 
to their culture to meet the demands of trout and 
salmon culture. Truly only in a very general way, 
until experiment determines the details of its applica- 
tion. [I am not in possession of any authentic evidence 
that salmonidae have been reared in ponds managed 
alter the Dubisch or any similar method. Yet there 
seems no good reason to doubt that it is quite feasible 
so to grow them, Trout have been grown very suc- 
