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hybrids between salmon and minnows, perches and bullheads, 
sticklebacks and carps, and were these hybrids to prove 
fertile, in a comparatively very short space of time all land 
marks would be obliterated; families, genera, and species 
would be things of the past. And if this did occur the result 
could be readily foretold, now small forms obtain sustenance in 
little as well as in large pieces of water; but were these small 
forms to merge into the larger, our brooks, our lesser streams, 
and ponds would no longer be stocked with fish for the size of 
the stream, and the amount of food would be insufficient 
to maintain them in health, even were it sufficient to 
sustain life. And could we hope for a hardy race from young 
raised under such conditions? Or even were our fishes entirely 
restricted to our larger rivers, what would occur? Predaceous 
forms of destroyers, perhaps man himself, would soon diminish 
and probably annihilate them. I shall presently have to show 
that deterioration in the size of parent fish may be equivalent 
to diminution in the size of the offspring, such being Nature’s 
method of preventing the extermination of the race. For 
decreasing their size will cause them to be less sought after, 
and it will only be when the larger fish are left for breeders 
that larger offspring result. In short, when man or other 
causes afford to fish sufficient protection, then Nature assists 
in improving the race; when man or other destructive factors 
ereedily kills all they are able, then the breed dwarfs, possibly 
to prevent its extermination. I will first inquire into what 
migrations fish undertake, either in the sea or in the fresh 
waters for the purpose of breeding; and, secondly, whether 
these migrations can be changed partially or entirely by ex- 
traneous causes ? 
To whichever division fish belong they are generally per- 
ceived at the commencement of their breeding season migrating 
to localities most suitable for the reception of their eggs, and 
the bringing forth of their young. The majority of marine 
forms seek banks, or are found nearer in shore or in shallower 
waters than such as they inhabit at other times. This arrival 
of gregarious kinds of mature fish occurs when they are ready 
-_—T SS «ee eee 
