The Zoologist — December, 1869. 1929 



Collected Observalions on British Reptiles. 

 By Edward Newman. 



(Continued from Zool. S. S. 1835). 



The Common Frog [Rana temporaria). 

 Rana temporaria, Linneus, Sysieina Natures, vol. i. p. 537. 



There seems to me an obvious difference between frogs and toads 

 in the character of the skin, that of frogs being moist like the mucous 

 surface of our own lips and tongue, as if from some natural and con- 

 tinuous exudation, while that of toads is dry and harsh to ihe touch, 

 often even making a slight rustling sound like that produced by 

 gently rubbing the surface of brown paper, I do not know how far 

 this superficial difference extends, that is to how many species or 

 so-called genera, but it is very apparent in those British species with 

 which we are familiar. The character is accompanied by a correspond- 

 ing one in economy, frogs appearing to prefer moist situations 

 generally within reach of water, and feeding by day ; while toads, for 

 the most part, frequent drier habitations, from which they emerge to 

 seek their prey by night : in accordance with this diurnal and noc- 

 turnal activity the stomach of frogs is invariably found to contain 

 sun-loving flies, especially of the genera Helophilus, Eristalis and 

 Musca, while that of the toad contains night-wandering beetles and 

 night-fljing moths. 



All authors agree as to the adaptability of this moist surface of the 

 frog's skin to purposes of respiration ; and all agree further as to the 

 existence of a cutaneous respiration ; but I am unable to quote a 

 single author who has made the subject clear to my own apprehension. 

 The idea originated with Spallanzani. The moist surface of the skin 

 is supposed to be the medium of this respiration, and the moisture is 

 said to be supplied from an internal reservoir, which Mr. Bell thus 

 describes : — "Every one knows that when a frog is hastily seized, or 

 even quickly pursued, it voids a considerable quantity of water, which 

 is generally but erroneously supposed to be the urine. This water 

 is limpid and pure, containing no traces of the usual elements of the 

 urinary secretion : it is contained in a sac, which has also been 

 mistakenly believed to be the urinary bladder. This is the reservoir 

 to which I have alluded. When, therefore, the frog is happily 

 placed in a damp atmosphere, or in water, the skin absorbs a quan- 

 tity of water, which there is every reason to believe is secreted 



second series — VOL. IV. 3 i» 



