TADPOLES 59 



ously, the renewal taking place by successive cells growing into 

 the bases of the older series. The shape and size differ much in 

 the various genera and species. The comb-like plates, composed of 

 those teeth which surround the lips, seem to be used chiefly for 

 the fixing or hooking of the food, while those which compose 

 the horny beak proper, the armature of the jaws, are used like 

 the radulae of snails. These beaks are likewise composed of a 

 great number of individual teeth, closely packed together in 

 several rows, but the teeth themselves are simple and not serrated. 



In Hyla arborea there are in all about 560 teeth. The 

 development of the mouth does not begin before the eleventh day ; 

 the horny teeth break through, and the jaws get black edges, on 

 the eighteenth. In Pelobates fuscus the number of horny teeth 

 is increased to about 1100. In Borborocoetes taeniatus the horny 

 teeth form series of five bells, which fit into each other like the 

 joints of a rattlesnake's tail. 



One of the most extraordinary kinds of tadpoles is that of 

 Megaloplirys montana. 1 Mr. Annandale (Skeat Expedition) found 

 it at Bukit Besar, Malay Peninsula, from 2000 to 3000 feet 

 above the level of the sea. The tadpoles (Fig. 11) were found 

 in the beginning of the month of May 1899 in sandy streams 

 and in pools of rain-water ; they floated in a vertical position, 

 the peculiar membranous funnel-shaped expansion of the lips 

 acting as surface-floats. The inside of the funnel is beset with 

 radiating series of little horny teeth, and the whole apparatus 

 is possibly used for scraping the under -surface of the leaves 

 of water-plants in search of food. Total length of the tadpoles 

 1 inch. 2 



The gills, the formation of the operculum, and the modifica- 

 tions of the branchial arterial arches have been described fully 

 on p. 43 ; those of the hyo-branchial skeleton on p. 31. Fusion 

 of the opercular fold with the skin of the neck, across the 

 branchial region, causes the head to become confluent with the 

 trunk (cf. Fig. 9, 3, p. 57). The body becomes oval, more or less 

 globular, and the alimentary canal is greatly elongated and stowed 

 away in the shape of a neat, very regular spiral, shining through 



1 M. Weber, Ann. Jard. Botun. Buitenzorg, Suppl. ii. 1898, p. f>. 



2 For "A Synopsis of the Tadpoles of European Batrachians," see Boulenjjrr, 

 P. Z. S. 1891, pp. 593-627, pis. xlv.-xlvii. ; also Bedriaga, "Tableaux synoptic^iies 

 pour servir a la determination des larves des Batraciens Urodeles," C. R. Ass. 

 Franc. Sci. ii. 1891, pp. 540-546. 



