M. Carbonnier, who practises crayfish culture on a large scale, gives some interesting facts bearing on this question in the work already cited. He says that, in the streams of France, there are two very distinct kinds of crayfishes—the red-clawed crayfish (L’Écrevisse à pieds rouges), and the white-clawed crayfish (L’Écrevisse à pieds blancs), and that the latter inhabit the swifter streams. In a piece of land converted into a crayfish farm, in which the white-clawed crayfish existed naturally in great abundance, 300,000 red-clawed crayfish were introduced in the course of five years; nevertheless, at the end of this time, no intermediate forms were to be seen, and the “pieds rouges” exhibited a marked superiority in size over the “pieds blancs.” M. Carbonnier, in fact, says that they were nearly twice as big. On the whole, the facts as at present known, seem to incline rather in favour of the conclusion that _A. torrentium_ and _A. nobilis_ are distinct species; in the sense that transitional forms have not been clearly made out, and that, possibly, they do not interbreed. * * * * * As I have already remarked, the very numerous {298} specimens of English and Irish crayfishes which have passed through my hands, have all presented the character of _Astacus torrentium_, with which also the description given in works of recognised authority coincides as far as it goes.[21] The same form is found in many parts of France, as far south as the Pyrenees, and it is met with as far east as Alsace and Switzerland. I have recently[22] been enabled, by the kindness of Dr. Bolivar, of Madrid, who sent me a number of crayfishes from the neighbourhood of that city, to satisfy myself that the Spanish peninsula contains crayfishes altogether similar to those of Britain, except that the subrostral spine is less developed. Further, I have no doubt that Dr. Heller[23] is right in his identification of the English crayfish with a form which he describes under the name of _A. saxatilis_. He says that it is especially abundant in Southern Europe, and that it occurs in Greece, in Dalmatia, in the islands of Cherso and Veglia, at Trieste, in the Lago di Garda, and at Genoa. Further, _Astacus torrentium_ appears to be widely distributed in North Germany. The eastern limit of this crayfish is uncertain; but, according to Kessler,[24] it does not occur within the limits of the Russian empire. {299} [21] See Bell. “British Stalk-eyed Crustacea,” p. 237. [22] Since the statement respecting the occurrence of crayfishes in Spain on p. 44 was printed. [23] “Die Crustaceen des Südlichen Europas,” 1863. [24] “Die Russischen Flusskrebse.” Bulletin de la Société Impériale des Naturalistes de Moscow, 1874. _Astacus torrentium_ appears to be particularly addicted to rapid highland streams and the turbid pools which they feed.