114 INTRODUCTION. 



by v. Mehely that, in the few localities where the two 

 species co-exist, intermediate specimens occur which 

 are no doubt to be regarded as hybrids. 



As to the supposed hybrids between Rana esculenta 

 and temporaria, noticed by Schlotthauber and others, 

 they are nothing but R. arvalis, a species which is in 

 many respects intermediate between the two supposed 

 parents, and with which the authors in question do 

 not seem to have been well acquainted. 



Hybrid embryos between Rana esculenta and R. 

 arvalis appear to have been recently obtained by W. 

 Gebhardt. 



So-called hybrids between Hyla arborea and II. 

 meridional is (bary tonus) , and Bufo viridis and B. 

 arabicus, obtained by Heron-Royer, are only mongrels, 

 as I do not consider the specific distinctions justified. 



