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Show 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 sucb 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 Palaearctic 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 locality 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 comprehensive 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 m y hands to a most minute examination and comparison. Although I have, unfortunately, failed in m y 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 18811, proved on the whole a failure. The two groups into which the species was divided are quite arbitrary ; the author's typical form appears to include part of R. ridi-bunda, and his var. lessonce evidently embraces specimens of the typical form. In various papers2 I have endeavoured to throw some light on the matter, and my contributions have been supplemented by Boettger and Wolterstorff. The latest work on the subject is from the pen of J. de Bedriaga 3, 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. = R. ridibunda, Pall., R. cachinnans, Pall., R. caucasica, Pall., 1 C. R. Assoc. Franij., Congres d'Oran, p. 680. Also Mon. Anf. An. Ital. p. 61 (1883). * Zoologist, 1884, pp. 220, 265; Proc. Zool. Soc. 1884, p. 573, pi. Iv., and 1885, p. 666, pi. xl. ' Bull. Soc. Mosc. 1889, p. 242. |