AQUATIC FROGS IN NORTH GERMANY. 221 



the forms of North Germany by recent remarks of Pfliiger.* 

 He observes that two distinct varieties occur near Berlin, the 

 typical form, and a larger one which he designates as' the 

 " Seefrosch," from its inhabiting the lake -like expansions of the 

 Elver Spree. A fisherman named Noack, who for years has been 

 supplying physiological institutes with these large frogs, con- 

 siders the two as distinct species, because he can unmistakably 

 distinguish them at first glance, and because they breed at 

 difi'erent times of the year. The "Seefrosch" is an earlier 

 breeder, having finished breeding at the end of May, at which time 

 the other kind commences. Pfliiger, who has obtained the larger 

 frog from Noack, regards them as distinct races, but does not 

 give any definite distinctive characters. Having myself applied 

 this spring to Noack, I have received from him 126 specimens, 

 which at first sight I separated into two distinguishable forms'. 

 On closer examination I find that they are really distinct, and 

 that the new kind belongs to Group 2 of Camerano, whereas 

 the typical form of Eosel has a strong metatarsal tubercle. I 

 find, moreover, other characters, which require careful working 

 out; for the present I will restrict myself to a comparative 

 diagnosis of the two subspecies which, notwithstanding its brevity, 

 will permit easy identification : — 



1. Ra7ia esculenta, typica.— Inner metatarsal tubercle com- 

 pressed, large, resembling that oi R. arvalis ; its length is four to 

 five millim., in specimens in which the inner toe, measured from 

 the metatarsal tubercle, averages nine to eleven millim. The black 

 marbling of the flanks, and of the hinder side of the thighs, 

 encloses more or less of bright yellow, 



2. Rana fortis.— Inner metatarsal tubercle small, elongate, 

 feebly prominent; its length is two to four millim., in specimens 

 in which the inner toe measures nine to twelve millim. No yellow 

 on the flanks or thighs. 



I may add that in general coloration specimens of each sub- 

 species vary more from one another than from the allied form ; 

 R. fortis is more constant in its coloration. The whole 

 physiognomy is difi'erent, so that, in spite of the great variation 

 of colour, persons unacquainted with Batrachological studies, and 

 ignorant of the characters on which the distinction of the two 



* Arch, fiir Physiol, xxix., p. 48, and xxxii., p. 522, 



