ANURA 



strongly dilated discs on the fingers and toes, e.g. Rana white- 

 headi, R. natatrix, and R. cavity mpanum of Borneo, R. jerboa of 

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

 Rhacophorus reinwardti}, and R. afghana of the Himalayan system. 

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

 for having 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. 1 In 

 the young larvae of Rana temporaria, 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 

 2 wall around the jaws, and 



FIG. lo.-i Front view of the mouth of a tad- divides into an upper and 



pole of Jtana temporaria, showing the trans- 

 verse rows of tiny horny teeth ; 2, three lower lip ; fuiTOWS appear 



GTe?to eh rnyteeth ' mUChmagnified ' (After on them > and between 



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 - 

 armature, and on the seventeenth day the mouth-apparatus has 

 reached the configuration typical of the tadpole, which is now 

 about 14 mm. long. The number of horny teeth in R. temporaria 

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

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

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

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



1 Zeitschr. iviss. Zool. xlix. 1889, p. 43. 



