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Show 670 MR. BOULENGER ON THE GERMAN RIVER-FROG. [June 16, spots ; never is any trace of yellow to be detected on that region nor at the axil and groin, a character which well distinguishes this form from the true R. esculenta. The lower surfaces are white, with greyish spots or marblings in specimens kept dry ; after long sojourn in water, these parts are abundantly spotted or largely marbled with black. The abundance and intensity of these spots is irrespective of sex, a remark which, contrary to the statement of many authors, applies also to R. esculenta. The iris is black, veined with gold, the latter pigment being in far lesser abundance than in R. esculenta. The vocal sacs, which do not differ in size or position from those of the typical form, are strongly pigmented with black, pale grey when swollen out. The examination of the skeleton has failed to reveal any constant peculiarities supplementing the external characters. Biological.-Not having had the privilege of observing this Frog in its haunts, I cannot do better than reproduce Prof. Pfliiger's remarks, which comprise all that is known at present on its habits :- " M y friend Prof. Zuntz had the kindness, on my application, to make inquiries from the fisherman Noack in Coepenik, who for years has been collecting the large R. esculenta for physiological laboratories in this and foreign countries. The large 'species,' as it is called by Noack, lives chiefly in the lakes of the Upper Spree and in lake-like expansions of its affluents. It is not found in marshes. The smaller ' species' occurs in great numbers in a small river near Coepenik. The two ' species ' are seldom found together in the same place. Noack regards the large R. esculenta as a distinct 'species' because it is not only larger, darker, and not of so bright a green, but because its habitus is more elongate. Noack asserts that the larger kind spawns about a fortnight earlier than the smaller one. The spawning-time begins normally in the middle of May, but occurred this year (1882) several weeks in advance. It is so far certain that this year the small R. esculenta spawned in the milder climate of Bonn in the beginning of June, and the large R. esculenta in the colder climate of Berlin in the beginning of May. There was certainly not a single breeding couple of the latter to be found in Berlin in the beginning of June, as I found out to m y regret" \ " For clearness' sake I propose to designate as ' Seefrosch' the large variety, which does not live in marshes but in the running water of the lake-like expansions of the Spree. As it is so well distinguished from the smaller race by its earlier spawning-time, its habitus, its skin, and its peculiar abode, that no specialist will confound it, it is very remarkable that the crossing-essays proved in every respect successful, thus affording so far no justification for making a new species " \ The author then relates his successful experiments of fecundation between the " Seefrosch," the eggs of which were ready to be laid on the 17th of May, 1883, and the smaller race from Bonn, the spawning of which commenced only on the 29th of the same month; and he concludes :- "The artificial fecundation therefore affords no support to the 1 Arch. f. Physiol, xxix. p. 67. 2 L. c. xxxii. p. 522. |
