PAIRING AND OVIPOSITION. 67 



The Natterjack toad, B. calandta, also often pairs on 

 land, and being a bad swimmer, and only spawning at 

 night, numbers in embrace may be found in the day- 

 time in holes on the banks, their presence being 

 revealed by their loud croak. The tree-frogs usually 

 pair only at night or in the evening. Thoroughly 

 aquatic species like Bombinator and Rana esculenta 

 resort, of course, to the water before mating. 



Alytes, the most terrestrial of European Batrachians, 

 pairs and oviposits on land. The female never goes 

 into the water, and the male contents himself with a 

 hip-bath for the purpose of releasing his progeny from 

 the egg-capsules entrusted to his care. 



Species differ greatly in the choice of a site for 

 their nursery. Alytes exercises the greatest judg- 

 ment, avoiding ponds or pools already largely stocked 

 with tadpoles of other species, or any water which is 

 not permanent. The common toad and the tree- 

 frog, also, are judicious in their choice, and their 

 offspring are never doomed through drying up of the 

 site selected, an eventuality which the common frog 

 and the Natterjack toad do not appear to be able to 

 foresee. The latter species especially often spawns 

 in roadside ditches and puddles of a most temporary 

 nature, although suitable places may be near by, and 

 we often find masses of tlieir young tadpoles accumu- 

 lated in a small hole with scarcely any water left, 

 exposed to the sun-rays, where they must perish unless 

 saved by a timely rainfall. Frost often destroys the 

 brood of the common frog. 



It has been observed by Heron-Royer, and 1 have 

 more than once been able to verify the fact, that 

 different species which breed in the same water some- 

 how manage to keep clear of each other. In a pond 

 near Paris the above-mentioned author found liana 

 temporaria occupying the north, and Avest, Sana agilis 

 and Bvfo vulgaris the north-east, Pelodytes pundatus 

 the south-east, and Hyla arhorea the south, east, and 

 west. In this country, where Rana temporaria and 



