56 Journal of Entomolopy 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 algte 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) Ailer 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, and 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 i|uilc n(|tjalic in habit, the green-frog lias about nine- 

 Icnlhs of its food non-aquatic and tlic bull-frog about three-fourths non-aquatic. 



Uy way of summary, then, the tadpoles of the species of .^nura 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 by great changes in the alimentary canal and mouth. 



