20 MR. O. A. nOULENGER ON THE 



of water in which to deposit its eggs, provided it be not brackish, 

 often spawning in temporary winter pools which are sure to dry- 

 up before the time at which the larvee have completed their 

 metamorphosis, or on the edge of a pond where, the level of the 

 water falling after dry weather, the egg-clumps remain stranded. 

 No doubt the frogs are attracted to the shallow, slanting borders 

 in preference to the deeper parts with abrupt banks by the 

 comparative warmth of the water under the sun-rays of late 

 winter or early spring, with the unfortunate result which may be 

 witnessed almost year after year in some places, when, following 

 a spell of dry weather, the borders of ponds are covered with the 

 stranded jelly-like masses of frog-spawn drying away in the sun 

 before the liberation of the larvte. On my country rambles in 

 the end of Mai-ch or beginning of April, I have often rescued 

 the progeny of many frogs by removing such doomed egg-masses 

 from these fatal bea,ches to deeper water close by, which the 

 mother would have chosen had she been gifted with the instinct 

 possessed by the Common Toad. 



The migrations of the Common Frog towards the water must 

 take place, to a great extent, in the autumn, as many, perhaps 

 the majority of individuals, hibernate buried deep in the mud at 

 the bottom of ponds, sluggish but not dormant as in some higher 

 animals. Some years ago, just before Christmas, after a period 

 of severe frost, which had lasted more than a week, I was walking 

 on the ice of a small and shallow pond in Belgium, when my 

 attention was drawn to a bright red creature, first taken for a 

 gold-fish, moving under the ice, which very nearly extended to 

 the bottom of the pond ; this was a Common Frog, and on looking 

 closer, I discovered hundreds of others, less conspicuous owing to 

 their yellowish, brown, or olive colour. Some were very handsome 

 specimens, which I wished to secure. A pick-axe was fetched 

 from a neighbouring farm and a hole made in the ice, through 

 which I could introduce my arm and reach the bottom ; but the 

 frogs were so active that they swam away and not one could be 

 caught. I decided to return to the pond after the thaw, which 

 I did, but no more frogs were to be seen ; they had evidently 

 retired to their hibernating-quarters in the mud and in holes 

 under water. The reason why they came out when the pond was 

 frozen nearly to the bottom, must be attributed to the reduced 

 oxygen in the water, which made the frogs, breathing as they do 

 under such conditions chiefly by the skin, feel uncomfortable and 

 desire to escape. 



The Common Frog is the earliest breeder among European 

 Batrachians, spawning taking place in the South of England 

 from between the end of January and the end of March, the date 

 depending almost entirely on the temperature and therefore 

 varying considerably from year to year. Should the winter be a 

 mild one, the breeding may be over by the middle of February ; 

 i-ecurrence of cold weather after the frogs have begun spawning 

 \wa.\ cause them to return to their winter-quarters, with the 



