66 INTRODUCTION. 



former (inhabiting the extreme south) from January 

 to October, the latter from the end of February or 

 beginning of March to the beginning of September. 



The time at which each species commences to pair 

 varies, as we have seen, with the temperature, for the 

 early breeders at least. Thus in the south of Europe 

 these would start from January, whilst in the north or 

 at corresponding altitudes in the mountains represen- 

 tatives of the same species would be compelled to wait 

 until the thaw has set in. Again, exceptionally pro- 

 longed winters may cause the individuals of a species 

 to be retarded in this operation, so as to bring them 

 together with others which, under normal circum- 

 stances, do not breed until some weeks later. But, 

 on the whole, our Batrachians may be arranged in the 

 following order, beginning with the most precocious : 



1. Discoglossus, liana teinporaria, B. arvalis. 



2. Bana a gills, Alytes. 



3. Bufo vulgaris, Belobates, Belodytes. 



4. Bufo viridis, Bufo calamita, Hyla, Bombinator, 



Bana esculent a. 



Taking the three British species as an example, 

 Rana temporaria in normal years with us breeds in 

 the beginning of March, Bufo vulgaris in the beginning 

 of April, and Bufo calamita from the middle of May ; 

 their nuptial periods do not even overlap. 



Leaving out the genus Alytes, which is altogether 

 exceptional in its mode of parturition, all our Batra- 

 chians are compelled to resort to the water for the 

 purpose of depositing their spawn. In some species, 

 such as our common frog, the males precede the 

 females, and may be found in winter in a semi-torpid 

 condition, but already attired in their full breeding 

 costume, at the bottom of pools thickly coated with 

 ice. The common toad travels long distances on land, 

 or following the course of brooks, in quest of suitable 

 breeding- places ; and if the sexes meet on the way the 

 male often secures immediate possession of the female, 

 accomplishing the rest of the journey on her back. 



