1891.] RACES OF RANA ESCULENTA. 375 



any knowledge of the intermediate forms, would unhesitatingly 

 pronounce them as representing distinct species : they have, in fact, 

 been referred to distinct genera by such experienced workers as 

 Peters and Cope. But if we pursue our investigations over the wide 

 area occupied by this Frog, viz, the whole of the Palsearctic Region, 

 we soon find all the differences by which we were at first struck to 

 blend through such a number of intermediate forms as to leave no 

 other course open but to maintain intact the Linnean species. 

 However, a great difficulty still remains to be dealt with : the 

 principal of the differences ascertained are not merely individual ; 

 nor are they entirely dependent on locaHty or climate, as almost 

 identical specimens are met with at such distant points as North 

 Germany, the Sahara, and Baluchistan. And, what is more striking 

 still, in the case of two forms occurring in the same country, they 

 may be perfectly separable and not interbreed, as has been shown 

 to be the case in Germany. It is therefore not serving the interest 

 of exact taxonomy and zoogeography to be satisfied with the com- 

 prehensive notion of Rana esculenta. Attempts should be, and have 

 been, made at a division of the specific type into races or subspecies. 

 With this object in view, I have, for the last few years, been 

 amassing material and information, and have subjected the many 

 hundreds of specimens which have passed through my hands to a most 

 minute examination and comparison. 



Although I have, unfortunately, failed in my attempt at drawing 

 very sharp demarcation lines between the various forms, 1 am still in 

 hopes that others may be more successful ; and with the object of 

 furnishing them with a basis for future researches, I venture to 

 publish the following notes, which at the same time show the extent 

 of the material upon which I have worked. 



The first attempt at subdividing Rana esculenta into subspecies, 

 published by Camerano in 1881 \ proved on the whole a failure. 

 The two groups into which the species was divided are quite arbi- 

 trary; the author's typical form appears to include part of 22. ridi- 

 bundoy and his var. lessonce evidently embraces specimens of the 

 typical form. In various papers '^ I have endeavoured to throw 

 some light on the matter, and my contributions have been supple- 

 mented by Boettger and WolterstorfiF. The latest work on the 

 subject is from the pen of J. de Bedriaga ^ who admits four forms 

 in Europe and Western Asia, or one more than I am able to recognize, 

 the Spanish-North- African specimens being regarded by him as 

 forming a subspecies distinct from R. ridibunda = fortis. 



I now propose to divide Rana esculenta into four principal forms, 

 viz. : — 



1. Var. RIDIBUNDA. 



= i2. ridibunda. Pall., R. cachinnans, Pall., R. caucasica. Pall., 



1 C. E.. Assoc. FraiKj., Congres d'Oran, p. 680. Also Mon. Anf. An. Ital. 

 p. 61 (1883). 



2 Zoologist, 1884, pp. 220, 265 ; Proc. Zool. Soc. 1884, p. 573, pi. Iv., and 



1885, p. 660, pi. xl. 

 ' Bull. Soc. Mosc. 1889, p. 242. 



