11 TADPOLES 59 



oiisly, the renewal taking place by successive cells growing into 

 the bases of the older series. The shape and size difl'er much in 

 the various genera iiiid s])ecies. The comb-like plates, composed ol" 

 those teeth whicli sunduiid the lips, seem to be used chiefly for 

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

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

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

 great number of individual teeth, closely packed together in 

 several rows, but the teeth themselves are simple and not sen'ated. 



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

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

 the hi any teeth break through, and the jaws get black edges, on 

 the eighteenth. In Felohates fuscus the numlDcr of horny teeth 

 is increased to about 1100. In Borborocoetes taeniatas 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 

 Mc(i((lop]i rys montana} Mr. Annandale (Skeat Expedition) found 

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

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

 in the bednnino- of the montli of May 1899 in sandv streams 

 and in pools of rain-water : they floated in a \ertical position, 

 the peculiar membranous funnel-shaped expansion of tlie lips 

 actinrj 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 incli.' 



Thf uills, the formation of tlie opercuhuu, and the modifica- 

 tions of the branchial arterial arches have been described fully 

 on ]i. 4:'. : those of the hyo-branchial skeleton on p. 31. Fusion 

 ctf Llie 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. ~u). The ])ody becomes oval, more or less 

 gloljular, and the alimentary canal is greatly elongated and stowed 

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



' M. WebiT, Ann. Jard. Jlulan. Buileiizortj, Sujiiil. ii. 1S9S, ii. '.. 



-' For "A Synop.sis of tlu' Tadpoles of European Batracliians," see Bouleiigor, 

 P. Z. ,S'. 1S91, pp. 593-G27, pis. xlv.-xlvii. ; also Bedriaga, "Tableaux synoptitjues 

 pour servir a la determination des larves des Batraciens Urodeles," C. /.'. Jss. 

 Franc. Sci. ii. ]891, pp. r.40-.'.4t). 



