Variation of the Edible Frog. 240 



inner metatarsal tubercle of the var. chinensis is remarkable 

 tor a certain mobility, the distal part of its base being- more 

 or less detached from the metatarsal of the inner toe with 

 which it is connected by a web-like membrane. This 

 character is not only inconstant in this variety, as I was able 

 to demonstrate to the second author by sending him for 

 identification a cut-off foot of a specimen from Broughton 

 Bay, Corea, which he returned to me named var. lessonce, 

 but it is also found in some specimens of the latter (from 

 Cambridgeshire and Norfolk) when the tubercle is very 

 strongly developed, a fact also observed by Fejervary * in 

 the case of his var. bolkayi from Switzerland ( = lessonce). 

 This character is correlative of the transformation of the 

 tubercle into a fossorial organ, as already recognised by 

 Wolterstorff, who fully admits the true state of things in the 

 var. chinensis, from a diagnostic point of view, although 

 unfortunately not acquainted with the amount of variation 

 in tiie var. lessonce. It has also been observed that the base 

 of the tubercle of the var. chinensis does not run parallel 

 to the axis of the longest toe, but is oblique to it ; this is 

 however only more or less so in the Chinese-Japanese frog, 

 again in relation with the degree of development of the 

 tubercle, and a similar disposition, varying in degree, is like- 

 wise to be observed in the var. lessoncr. 



Although the metatarsal tubercle may be identical in the 

 two varieties, I quite agree with Wolterstorff, and have 

 always held the view that the var. chinensis cannot have 

 been derived from the var. lessonce, the two forms repre- 

 senting independent extremes in the parallel evolution of the 

 same adaptive character ; but the var. lessonce is there to 

 illustrate the steps through which the character has been 

 evolved out of a type such as the var. ridibunda, now so 

 completely separated from the easternmost form of R. escu- 

 lenta. Wolterstorff seems to look upon the typical form, or 

 rather its hypothetical direct ancestor, as the origin of the 

 races in question ; Bolkay, in my opinion, is nearer the 

 truth when he suggests R. ridibunda being nearer to 

 R. chinensis, but at the same time he inverts the drift of 

 evolution in regarding the former as derived from the latter, 

 owing to theoretical considerations based on the now ex- 

 ploded " prsepollex " and " prsehallux " theory. 



In his description of R. nigromaculata (chinensis), Stej- 

 neger says the toes are about f webbed. It is so in some 

 cases, but rather the exception than the rule, and similar 



* Beitr. Herp. Rhonetal, p, 20 (1909). 



