56 Journal of Entomology and Zoology 
In each species studied the same general tendencies are evident: ((1) The larval 
alimentary canal is very long, but slightly differentiated in its various portions, and 
filled with ooze and mud scraped up from objects in the pond and containing many 
forms of diatoms, blue-green and green alge of. filamentous and non-filamentous 
types, small pieces of plant tissue, and bits of fiber and other slowly decaying material 
to be found in ooze. Very few tadpoles were found with any animal food, the excep- 
tions having a few small Crustacea, Protozoa and Rotifera. 
(2) After both pairs of legs are evident and the horny plates of the tadpole 
mouth are shed, the tail is found to be gradually absorbed and the alimentary canal 
decreases to about one-tenth of its larval length at the same time that it widens 
anteriorly to form the stomach and posteriorly to form the large intestine. During 
this transformation period the mouth increases to about six or seven times its former 
size and there is practically no feeding done. The epidermis is apparently shed 
rather frequently as the tail is being absorbed; for its presence in the alimentary canal 
during the final stages of transformation is so frequent as to be quite universal in the 
larger species and occurs in all those studied. 
(3) After these changes have been just about completed the young frog or toad 
begins life as a carnivor, apparently taking anything movable yet small enough for it 
to handle. Occasional bits of plant-down and small feathers testify to the attractive- 
ness of a moving object. Almost all groups of invertebrates and some vertebrates are 
represented in the diet, the largest per cent being insects, crustaceans, spiders, sow- 
bugs, and snails. Some individuals do contain pieces of plant tissue, sand, mud, and 
other inactive objects, but these seem to be accidental, often occurring where ground 
beetles or similar forms have been eaten. 
(4) The newly transformed individuals show a decided tendency toward the 
habits of the adults; the toad, tree-toad, aud peeper eating almost nothing of an 
aquatic nature; the meadow-frog, pickerel-frog, and wood-frog eating some aquatic 
forms, a few per cent more than do the adults of their species; of the other two species, 
both of which are considered quite aquatic in habit, the green-frog has about nine- 
tenths of its food non-aquatic and the bull-frog about three-fourths non-aquatic. 
By way of summary, then, the tadpoles of the species of Anura studied for this 
paper are largely herbivorous, the transforming individuals do almost no feeding, 
and the young frogs or toads are mostly carnivorous. ‘These changes in habit are 
made possible hy great changes in the alimentary canal and mouth. 
