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Some valuable fishes may be found dependent on food too liable to in- 
jury or destruction by man or nature, to make it worth while to cultivate 
them, while others, equally valuable, may be proven to subsist on food 
practically indestructible. 
Such species as eat mixed food, so that, in case of scarcity of one kind, 
another may be drawn upon, are evidently more promising, other things be- 
ing equal, than those of a more limited diet. 
That a full understanding of the competitions among the fishes of a 
stream or lake is necessary to anything better than guess-work in fish-cul- 
ture, or an expensive and improvident trusting to luck, is evident at once. * 
The scavenger fishes, which, by devouring the filth of streams, help to 
purify them, are doubtless worthy of recognition. Whether a filth-eating 
fish is better or healthier food than a bird or a mammal of similar habits, 
may, perhaps, be profitably discussed. 
An acquaintance with the subject sufficient for the purposes above 
mentioned must, of course, include the whole life of the fish, at all ages and 
in all seasons. It is not impossible, for example, that the draining of stag- 
nant waters connected with a stream may unfavorably affect some of its 
fishes, by lessening the supply of JEntomostraca, especially Cladocera , for the 
food of the fry. 
So much may properly be said concerning the purpose and promise of 
the research, to justify the labor given to it, — especially since the general 
neglect it has received may seem to indicate that it is not worth elaborate 
study. 
METHODS. 
The stomachs and intestines were taken out of the fishes just as these 
came from the seine ; were labeled with specific name, place and date, and 
preserved in strong alcohol. They were afterward opened and the contents 
examined (usually with the microscope). Notes were made upon the objects 
found in each, as far as they were recognizable — the species being deter- 
mined, if possible, otherwise the genus, family, order, or even only the class. 
The contents of each stomach were then bottled separately in alcohol, 
labeled and preserved for future verification and further study. The emp- 
tied stomachs have also been kept for anatomical purposes, and as a means 
of verifying the species. It was found unnecessary to remove the stomachs 
of the minnows, as these were well enough preserved in the bodies of the 
fishes themselves. 
* That fishes and land birds should ever come into competition, seems at first 
sight remarkable ; nevertheless some of the former eat large numbers of land 
insects which fall into the water. The supply of these would, of course, be limited 
by the depredations of birds. 
