506 Records of the Indian Museum. [Vol. XXIV, 



in the Microhyla by soft ridges. Moreover, it is much more evi- 

 dent in the latter tadpole than in the former that the whole 

 float is formed by a hypertrophy of the lower lip. Similarly in 

 the Helophryne and the Bufo there is a structural difference, only 

 to be observed on close examination. The sucker of the Bufo is 

 formed (much in thesa:ne general way as the float of M. achatina 

 but correlated with an entirely different function) by a hyper- 

 trophy of the lower lip, while in the Helophryne both lips are 

 equally developed. 



In this respect the Helophryne closely resembles an unidenti- 

 fied larva discussed by one J of us from the Malabar Zone of 

 Peninsular India. Indeed the structural analogy is so close that 

 it does not seem too much to claim that there is also a homology, 

 in other words that a genetic affinity exists.' We can claim genetic 

 affinity only between those tadpoles in which similar structures are 

 present with a similar function and produced by the same modifica- 

 tions of structures or organs common to widely different forms, but 

 when these conditions occur to such a degree as to produce morpho- 

 logical identity it is not extravagant to do so. 



Suckers may be produced by the evolution of a new organ, 

 as in the species of Rana described later, or by hypertrophy 

 of the lips, as in the tadpoles of the Helophryne and the Bufo 

 discussed above. In the latter instance many different stages in 

 the evolution of the perfect structure are known. 8 But in species 

 like Rana afghana the peculiar structure seems, so far as our 

 present knowledge goes, to have arisen strictly de novo. That 

 it has really done so is of course improbable, but the earlier 

 stages have not been discovered and have perhaps been eliminated. 

 There is no evidence for any homology between the adhesive 

 apparatus and that found on the ventral surface of all very } 7 oung 

 Batrachian larvae.* 



It has been observed by one of us both in the Khasi Hills 

 and the Nilgiris that the tadpoles abundant in the large pools of 

 hill-streams, at spots at which the current is not rapid, belong to 

 quite a different type from any we have mentioned, being very 

 large and stout, with powerful tails, comparatively small mouths, 

 no marked structural peculiarities of an obviously adaptive nature 

 and either a very conspicuous or a very dense pigmentation. Good 

 examples of this type are the tadpoles of Rana ulticola b in Assam 

 and of R. malabarica in South India. The former has a conspicu- 

 ous black ocellus on the tail and possesses parotid glands which 

 produce an abundant secretion on irritation. The latter are of a 



I Annandale, Rec. Ind. Mus. XV, p. 22, pi. 1, figs. 6, 6a (1918). 



1 No frog of the family Cystignathidae is known from the Oriental Region, 

 but the Batrachia of the hills of the Malabar Zone are still imperfectly studied 

 and the adult of this tadpole is a burrowing form and, therefore, liable to escape 

 notice. The Ethiopian affinities of the fauna of the Malabar Zone are well re- 

 cognised by Zoogeographers. 



8 Annandale, Rec. Ind. Mus. VIII, p. 19 (1912). 



* Boulenger, Rec. Ind. Mus. XX, pp. ioo, 168 (1920). 



i Thiele, Zeitsch. wiss. Zool. XLVI, p. 75, pi. x, fig. 6 (1888). 



