30 THE DEVELOPMENT 



that, although many of the protococci were swallowed, yet it is very 

 problematical whether any nourishments was obtained from them, 

 as numbers were found retaining their green colour, and appar- 

 ently intact even after passing through the alimentary canal. 



What, then, may be asked, is the force of the statement that 

 the tadpole "crops the green herbage of the water-plants," and 

 that its spirally convoluted intestine is well fitted for the digestion 

 of vegetable matter? Do they or do they not crop green vegetable 

 matter? We have seen that where much animal nourishment is 

 not forthcoming, the tadpole will forage for food amongst vegeta- 

 ble matter, and in some instances isolated animals may be seen 

 apparently cropping at morsels of duck-weed. Many times have 

 I examined portions of the duck-weed leaf, thus apparently 

 attacked, to see if any morsels had been eaten, but was never able 

 to observe anything of the kind. 



At last, however, a few animals kept by themselves, in a bottle 

 of clean water and only supplied occasionally with food, solved 

 the riddle for me. On the sides of this bottle there gradually 

 appeared numerous white specks having all the appearance of 

 microscopic fungi, which the tadpoles attacked and ate readily. 

 In every instance these white specks proved to consist of colonies 

 of Vorticella attached to the glass by means of their long pedun- 

 cles, the tadpoles, having nothing better to eat, fell upon and 

 devoured these colonies. Turning, then, my attention again to 

 an animal in the act of apparently cropping green vegetable 

 matter, I found colonies of Vorticella attached to the same frond, 

 so that the conclusion to be drawn from these facts appears to be 

 that the tadpole is a most omnivorous creature, devouring almost 

 everything that comes in its way in the shape of dead or decom- 

 posing animal and vegetable matter, and in default of this its 

 natural food is quite willing to content itself with any of the more 

 minute and even miscroscopic creatures it meets in the water. 

 Green food, however, except in the most finely divided state, it 

 cannot eat, and,~ as I hope to show in a future paper, its teeth, 

 when they appear, are carnivorous rather than herbivorous. 



In the sections given herewith, which illustrate the formation 

 of the mouth when first opened, it will be seen that this consists 

 of a wide and elongated sac, armed with prehensile lips. An 



