Pomona College, Claremont, California 51 
Table 8. Data for Bufo americanus---Continued 
No. Body Tail Mouth Ali. Can. Fore Legs Tot FOOD 
24 10 2 ae er oy 12 id 3 Nothing identifiable 
25 9 2 “A ae 12 if 3 Epidermis 
26 10 1 st Ke 13 oe 3 epidermis 
27 10 1 : : 11 fo 3 Nothing identifiable 
28 10 5 a ‘ 13 “ 3 Epidermis ? 
29 11 5 SA ‘ 13 . 3 Mud with Navicula, masses of Pleuro- 
coccus 
30 9 0 se oi ue 13 as 2  Physopoda 1, Insecta 1 
31 11 5 of # 13 . ai Pulmonata 1 
32 » 10 0 f ‘ 4 16 ss 3 Epidermis, iptera larva 
33 11 0 e fs 13 s 3 Collembola 2 
34 11 0 ee ‘ e 12 ae 3 Nothing identifiable 
35 11 0 s f 12 oe 3 Nothing 
36 10 ne ne Y oe 10 Ae 3 IEpidermis 
37 10 0 10 ce 3. Epidermis, Diptera 1 
38 10 0 ‘ ‘ 11 g 3 Nothing 
39 9 0 ae 10 oy 3 Nothing 
40 10 0 us 10 ‘ss 3. Epidermis 
Comparison of Tadpoles of the Various Species. 
In the eight species used the tadpoles agree in being for the most part herbivorous. 
The small mouth is provided with horny jaws and is used largely in nibbling off 
Algae, bits of moss, and other plants, and in gathering up masses of ooze and mud 
with the many diatoms and desmids to be found in such situations, and the occasional 
Protozoa of the Difflugia and Arcella types. 
Very often one sees statements such as made by Miss Dickerson that tadpoles, 
especially of some species, are very “fond of any animal food available. Thus these 
tadpoles act as scavengers and dispose of dead fish or dead tadpoles even, that would 
otherwise become a menace to the living creatures of the pond.’ ‘These statements 
might indeed be made by almost anyone who has observed tadpoles to any extent. I 
remember when a boy of reading that a good way of cleaning a skeleton of a small 
animal like a mouse was to place it in a pond containing many tadpoles and it would 
soon be nicely freed from the flesh. Experiment showed this to be more or less true; 
but although I have studied many tadpoles in the series of forms now being discussed, 
and although these come from many different ponds, the fact that in no case was such 
animal matter found, leads me to believe that it is not so important a source of 
food to the tadpole as is commonly believed. 
Since all the tadpoles of the various species are aquatic and therefore in rather 
uniform conditions, one would not expect their food to vary as much as does that of 
the transformed individuals. The alimentary canal is invariably very long, in keeping 
with the herbivorous habits; but almost entirely undifferentiated, no stomach nor 
large intestine being evident. As long as the tadpole mouth is present the alimentary 
canal is almost always filled with ooze and silt, a great part of which is inorganic. 
Since the size of the mouth varies considerably with the species, one would expect it 
to allow of more variation in food-habit than does any other one factor. I was par- 
ticularly interested, therefore, to see what the largest animal form taken would be 
and in which species it would be found. Unfortunately I did not have a very good 
series of specimens with the tadpole mouth in the large bull-frog and green-frog, but 
those examined showed almost no variation from the smaller species. One green-frog 
did have a small crustacean (Ceriodaphnia?), a meadow-frog contained a rotifer 
(Anurea), another had a crustacean (Cypridopsis), and a peeper was found with 
