436 ANIMAL LIFE-HISTORIES 



regarded as a permanent larva, though one that has acquired the 

 power of laying eggs. This peculiar state of things has come 

 about in the absence of surroundings suitable for life on land. 

 When such surroundings exist the Axolotl does become adult, and 

 is then a kind of salamander. 



A few Urodeles are viviparous, development taking place 

 internally. This is the case, for example, in the Spotted Sala- 

 mander (Salamandra maculosa), which does not lay eggs, but 

 produces a brood of tadpoles. The Black Salamander (S. atra) 

 of the Alpine region is also viviparous, and produces only a couple 

 of young, which make their appearance in the world as minute 

 facsimiles of their parents, though they pass through a tadpole 

 stage before they are born. What has been said above about 

 Autodax (p. 435) applies to this case also, except that develop- 

 ment is internal instead of being external. The small number of 

 young produced by the Black Salamander is clearly in relation to 

 an improved chance of individual survival resulting from the 

 sheltered nature of the development. It appears, however, that 

 a great many eggs are actually formed, though the large majority 

 of them disintegrate and serve as food for the two which are 

 destined to perpetuate the species. 



TAILLESS AMPHIBIANS (ANURA). - -The Frogs and Toads 

 which make up this group are very specialized creatures, which 

 differ remarkably among one another in respect of egg-laying and 

 care of eggs. 



In the majority of cases a very large number of comparatively 

 small eggs are produced, from which typical tadpoles hatch out 

 that are but ill adapted to cope successfully with the many 

 dangers to which they are exposed. Relatively few of them 

 become adult, and extreme fecundity alone prevents such species 

 from becoming extinct. Comparison may be made with fishes in 

 this respect (see p. 425). In average cases the eggs are laid in 

 water, familiar instances being afforded by the Common Toad 

 (Bufo vulgaris] and the Grass Frog (Rana temper aria), the jelly- 

 like spawn of the former consisting of long cylindrical strings, 

 while that of the latter is in the form of irregular clumps. Both 

 kinds are to be seen floating in our ponds and ditches in early 

 spring, quite uncared for by the parents, though not altogether 

 unprotected. Examination of frog-spawn will show that each of 

 the black shot-like eggs is inclosed in a sphere of jelly, which is 



