Temperature and Rate of Development of the Eggs of British Anura

A general account of past work on temperature in relation to amphibian morphogenesis is provided by Moore (I939), who gives also a fuller bibliography. The present paper is an attempt to apply the conclusions of his work, which is based on American Amphibia, especially five species of Rana, to certain British species. All individuals were obtained in the south of England: the common frog, Rana temporaria L., from the Lea Valley, the common toad, Bufo bufo (L.), from Richmond Park, and the edible frog, Rana esculenta L. forma typica, from West Kent. The habits of the three species differ considerably; Rana temporaria is moderately aquatic, but will wander some distance from water; Bufo bufo is aquatic only in the breeding season and is seldom to be taken in water during the summer; Rana esculenta, however, is the most aquatic of all the European Ranidae, being rarely found more than a few feet from the edge of a pond. The species are not very clearly related, Rana being firmisternous and Bufo arciferous: Rana temporaria and R. esculenta are probably the most distantly related European species of their genus. All three species are very widely distributed indeed, and are very common. R. esculenta is local in Britain, and is usually considered to have been introduced (cf. Smith, I939).