670 MR. BOULENGER ON THE GERMAN RIVER-FROG. [JlUie 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 : — 



" My 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 

 }ilace. 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 beginninjj 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 my regret" \ 



" For clearness' sake I propose to designate as ' Seefrosch ' the 

 large variety, »l)ich dues 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 l/th 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 

 ' Arch. f. Pliysiol. xxix. p. 67. " L. c. xxxii. p. 522. 



