THE SYSTEMATIC VALUE OF RANA CHLNENSIS OSBECK 79 



var. lessonce, lies in the fact that it is never parallel to the length axis 

 of sole, but invariably closes on it at a larger or smaller angle, and that 

 it never stands vertically on the surface of sole but always so to say 

 leans against it. The most striking difference, however, is — as also 

 Wolterstorff already recorded — the fact of the meta-tarsal tuber- 

 cle not adhering to the base of thumb, being independently movable 

 and that of a web extending between it and the thumb. The above 

 also justifies Osbeck's statement of the Chinese water-frog having 

 six toes as in this case the meta-tarsal tubercle can truly be con- 

 sidered as a sixth toe transformed into a burrowing implement. 

 The edge of the meta-tarsal tubercle is very sharp on the Peking 

 andTsingtau specimens and quite resembles the meta-tarsal tubercle 

 of Pelobates fuscus. This edge is never as sharp on the Pingshiang, 

 Kiukiang and Japan specimens. 



The dimensions of the meta-tarsal tubercle frequently vary on 

 specimens from Peking and Tsingtau; it attains the length of the 

 thumb ; on specimens collected at other places it is a good deal shorter, 

 but it is never contained twice in the length of the thumb. As 

 regards its role in biology, this peculiarity is in itself reason enough 

 for R. chinensis to be separated as an independent species. 



Once their pools dried up, our esculenta and ridibunda generally 

 wander further on in search of new waters. Not so with R. chinensis 

 which burrows itself in the ground as soon as water is wanting. 

 Dr. Kreyenberg (17, p. 136) at Tsingtau, found frogs burrowed 

 under the ground and he writes further on about the Chinese frog 

 digging itself under the earth on the rice fields once the water there 

 has dried up. 



It is interesting to notice here that these frogs do not bury them- 

 selves thus in exceptional cases, but do this regularly with the be- 

 ginning of the dry season; this being recorded from the surroundings 

 of Peking and Tsingtau most likely happens elsewhere also and 

 seems sufficient explanation of the fact that the meta-tarsal tubercle 

 on the specimens from the above named places is so particularly 

 well developed and so excellent a burrowing implement. It is not 

 improbable that in some parts of those countries this burrowing is 

 only exceptional (the specimens of Kiukiang and Pingshiang do 

 not present so sharp a meta-tarsal tubercle) and it is most likely 



