286 FROGS, TOADS, AND NEWTS [CH. VIII 



covered with cilia, which keep the water round the 

 tadpole in constant motion, and thereby assist respiration. 

 Upon the ventral surface of the head is a horseshoe 

 shaped structure commonly called the sucker, but in 

 reality consisting of a mass of mucous glands by whose 

 secretion the animal attaches itself to weeds and other 

 objects. If a clean needle or fine glass rod be presented 

 to a tadpole removed from the water the creature will 

 readily adhere to it and subsequently a deposit of mucus 

 can be seen upon the surface by the aid of a microscope. 

 There is no mouth present until the tadpole has been 

 hatched a few days. Notwithstanding this fact there is 

 a decided increase in size ; possibly food may be absorbed 

 by the " suckers." When the perforation is effected the 

 mouth is furnished with a pair of horny jaws and fringing 

 lips. The tadpole now begins for the first time to take 

 food for itself, its diet consisting of the leaves of water 

 weeds and other vegetable matter. The alimentary canal 

 grows rapidly and attains a great length so that it 

 falls into several close coils within the abdomen. The 

 direction of the coiling is not continuously the same; 

 about one and a half turns take place " counter-clockwise," 

 and about the same number " clockwise," the spiral being 

 reversed near the middle of its course. The reversed 

 spiral is a mechanical necessity when a tube whose ends 

 are not free to revolve is thrown into coils. Eventually 

 the canal becomes actually longer than it is in the young 

 frog. 



If examined under the microscope at this stage the 

 gills are seen to be nearly transparent tubes with a solid 



