AMPHIBIANS 



435 



a time to water-plants by means of threads that project from the 

 upper jaw. 



Among other species of newt-like animals there may be more 

 elaborate provision for the welfare of the eggs. These may be 

 moored to stones by means of threads into which their invest- 

 ments are drawn out, as in one of the forms native to eastern 

 North America (Spelerpes bilineahis); others again are deposited 

 in little bags hung up on water-plants, as in a West Siberian 

 species {Salamandrella Keyserlingi). Instances have also been 

 described of maternal solicitude. The eel-like Three-toed Sala- 

 mander {Atnpkiuma means) of the south-eastern United States, 

 for example, coils her body round the string of eggs, which hatch 

 out into tadpoles about three 

 months later. In one little newt 

 {Desmognathus fuscus, fig. 960), 

 native to the east of North 

 America, the stalked eggs are M 

 fixed to the body of the mother, 

 who shelters in a hole during 

 their development. Part of the 

 tadpole -stage in the life -history 

 is here passed through within the 

 egg. This prepares us for what takes place in a form i^Autodax 

 lugubris) which lives in the western part of North America. The 

 adult is entirely terrestrial, and the female retires to a hole under- 

 ground for the purpose of laying her eggs, each of which is fixed 

 to a bit of earth by means of a thread. They number about a 

 score, and when all are deposited the mother coils herself round 

 them until such time as they hatch out, a fortnight or three weeks 

 later. The tadpole-stage is passed through entirely within the 

 ^gg, and the young closely resemble their parents except in size 

 and colour. This reminds us of the life-history of the slug 

 Onchidium, where there is no free-living larva, although this is 

 well represented before hatching (see p. 414). Such a life-history 

 is intelligible when regarded as an adaptation to life on land, with 

 entire abandonment of aquatic existence. 



The famous case of the Axolotl, mentioned elsewhere (see vol. 

 i, p. 249) is the exact reverse of what has just been described. 

 For here the adult stage under certain conditions is entirely sup- 

 pressed, and the animal remains a tadpole. It may therefore be 



Fig. 960. — Female Desmognathus /^tscus with her eggs 



