276 THE AMERICAN MONTHLY [Oct 
action of chemicals, especially acids, and did not seem to 
yield well to either soap, benzine, or alcohol. 
The investigation was, therefore, not altogether so satis- 
factory asI could wish; but was sufficiently so to estab- 
lish the main points, and to prove that their food consists 
very largely of diatoms, mostly Navicule, of the radiosa 
type; of which I was able to makea very satisfactory ex- 
amination, to be referred to again further on. There 
were also many starch grains, shown by the polariscope 
to be those of the potato, and about as many, perhaps, 
which were smaller, and possibly derived from bits of 
bread. There were also a number of green bodies of 
roundish contour, which were without much doubt des- 
mids. They had been too long subjected to the action of 
the gastric secretions for the species to be exactly made 
out, but they were probably Cosmariums of some sort; 
and their numbers were apparently too small for them 
to have formed a very important part of the fish’s diet. 
About a dozen grains of corn-smut were met with, all in 
one place. | 
-There was a very considerable quantity of white sand 
in the stomach and intestines, hardly any field of view 
in the microscope one-fiftieth of an inch in diameter be- 
ing without a number of grains of it. They were gener-— 
ally of about the same size as ordinary river sand, and 
polarized equally well. In one field of the size mentioned 
above there were thirteen grains of it, in another nine, 
and in a third five, of three taken at random. It may be 
possible, though hardly probable, that this sand was swal- 
lowed accidentally. It is, however, far more likely that 
it was swallowed designedly, to aid the process of diges- 
tion, as is the case with birds; and the size of these sand 
grains would, considering the difference in size of the two 
creatures, apparently bear a just proportion to the little 
stones swallowed for this purpose by fowls. 
They may also have been swallowed to act by their 
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