LIFE OF AMPHIBIANS 



68 1 





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gil's which are pressed against the vascular wall of the uterus. It is 

 said that the respiration (and nutrition) of the young is helped by 

 crowds of red blood corpuscles which are discharged from the walls 

 of the uterus ; the debris of unsuccessful eggs and embryos seems also 

 to be used for food. 



Species of Hylodes, such as H. martinicensis of the West Indian 

 Islands, live in regions where there are few pools. In such cases the 

 development is completed within the egg-case, and a lung-breathing 

 tailed larva is hatched in about fourteen days. 



In some Mexican and N. American lakes there is an interesting 

 amphibian known as Ambly stoma or Siredon. It has two forms — one 

 losing its gills {Ambly stoma), the other retaining them (Axolotl). Both 

 these forms reproduce, and both may occur in the same lake. Formerly 

 they were referred to different genera. But the fact that some 

 Axolotls kept in the Jardin des Plantes in Paris lost their gills when 

 their surroundings were allowed to become less moist than usual, led 

 naturalists to recognise that the 

 two forms were but different 

 phases of one species. It has 

 been shown repeatedly that a 

 gilled Axolotl may be trans- 

 formed into a form without gills ; 

 and this metamorphosis seems to 

 occur constantly in one of the 

 Rocky Mountain lakes. Abund- 

 ant food and moisture favour the 

 persistence of the Axolotl stage. 



Amphibians are very defence- 

 less, but their colours often 

 conceal them. Not a few have 

 considerable power of colour- 

 change. The secretion of the 

 skin is often nauseous, and 

 therefore protective. In a few 



cases, such as Ceratophrys dorsata, there is a bony shield on the 

 back made of a number of small pieces arising as ossifications of the 

 inner stratum of the dermis and of the subcutaneous connective tissue. 

 It is interesting to notice the occurrence of numerous hair-like filaments 

 on the sides and thighs of the males of a Kamerun frog {Astylosternus 

 rohustus). 



Many Amphibians live alone, but they usually congregate at the 

 breeding seasons, when the amorous males often croak noisily. Alike 

 in their love and their hunger, they are most active in the twilight. 



Their food usually consists of worms, insects, slugs, and other small 

 animals, but some of the larval forms are for a time vegetarian in diet. 

 They are able to survive prolonged fasting, and many hibernate in 

 the mud. Though the familiar tales of " toads within stones " are for 

 the most part inaccurate, there is no doubt that both frogs and toads 

 can survive prolonged imprisonment. Besides having great vital 

 tenacity. Amphibians have considerable power of repairing injuries to 

 the tail or limbs. 



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Fig 



393. — Caecilian {Ichthyophis) 

 with eggs. — After Sarasin. 



