5! 



ANURA 



Strongly dilated discs on the fingers and toes, e.g. Rana loMU- 

 hmdl, Jl. nutatrix, and J,', cavikjmpanum of Borneo, B. jerboa of 

 Java (this larva was orighially described and figured as that of 

 FJutcophoriis reimanrlti), and 1!. afghana of the Himalayan system. 

 These tadpoles, at least those of R. jerboa, are further remarkable 

 for ha\'ing the " spiracular " opening very far back on the left 

 side, nearer to the base of the tail than to the snout, so as to be 

 well out of the way when the creature has attached itself by the 

 adhesive disc. 



The mouth of the tadpoles of Anura is furnished with horny 

 armaments, substitutes for teeth. Their development and that 

 of the mouth in general has been well described by Gutzeit.^ In 

 the young larvae of Rana tniipyrarin, one or two days after 

 hatching, a shallow groove appears above the conspicuous pair of 



adhesive organs. The groove 

 becomes rhombic in outline, 

 and when the mouth has 

 been formed in its centre, 

 the jaws appear in the 

 median corners of the 

 rhombus. The epidermis 

 then rises like a circular 

 wall around the jaws, and 



Fig. 10.^1, Front view of the mouth of a tad- divides into an upper and 

 pole of Puiim tem.porafui, showing tlie trans- i . n 



ver.se rows of tiny horny teeth ; 2, three lower lip ; turroWS appear 



successive horny teeth, much magnified. (After ^^^ them and between 

 Gntzeit.) .' . 



these various papillae and 

 comb-like transverse plates of teeth. The papillae are pos- 

 sibly tactile organs, but although nerves enter them, nerve- 

 endings of a sensory nature have not yet been discovered. 

 On the fourth day the jaws become black, by the tenth day 

 horny teeth have appeared upon all the plates of the mouth- 

 armatin-e, and on the seventeenth day the mouth-apparatus has 

 reached the configuration typical of the tadpole, which is now 

 about 1 4 mm. long. The number of horny teeth in R. terwporaria 

 amounts to about 640. These teeth are not euticular products, 

 but (Mjrnified cells ; they are very small, and consist each of one 

 Iiorny cell, which is shaped like a nightcap, the apex of which is 

 curved back and serrated. The little teeth are shed continu- 



' Zeitsdir. viss. Znol. xli.x. 1889, p. 4-3. 



