306 CLASS AMPHIBIA. 



distance," the young of many species with balancers, 4 fingers, 5 toea 

 free or webbed, limbs well developed except in the worm-like Sp. 

 parvipes (Orizaba) and iwiformis (Costa Rica), several species are 

 lungless, 20 species, N. and C. Amer., N.W. South Amer. (3 species), 

 Hayti (l.species), Eur. (1 species). Manculus Cope, N. Amer., with 

 4 toes, tongue as in preceding ; Anaides Baird (Autodax), tongue 

 cannot be protruded, 5 toes, N. Amer., A. luguhris Hallow., 

 entirely terrestrial, lungless, eggs laid in ground and whole develop- 

 ment passed through in the egg, embryo with external gills ; 

 Plethodon Tschudi, N. Amer., tongue as in last, 5 toes ; Batrachoseps 

 Bonap., tongue as in last. 4 toes, N. Amer. 



Sub-fam. 3. Amblystomatinae. Series of palatal teeth transvei'se 

 or posteriorly converging, on posterior portion of vomers ; parasphe- 

 noid toothless ; vertebrae amphicoelous, toes 4 or 5, N. Amer., N. 

 Asia. Hynohius Tschudi, 5 toes, Japan ; Salamandrella Dyb., 4 toes, 

 E. Siberia. Onychodactylns Tschudi, fingers (4) and toes (5) with 

 black claws, Japan ; Ranidena Kessler, 5 toes, E. temp. Asia ; 

 Batrachyperiis Boul., 4 toes, China ; Dicamptodon Strauch, California ; 

 Amblystoma Tschudi, palatal teeth in a nearly straight transverse 

 line or an angle, not separated in the middle by a wide interspace, 

 5 toes, N. and C. Amer., and 1 species (A. persiniile) in Siam ; A. 

 talpoideum Holbr. runs in light soils like a mole, S.E. Un. States ; 

 A tigrinum, Green, Un. States and Mexico, the larva is the axolotl, 

 which was fornaerly thought to be an adult form and called Siredoti 

 {S. axolotl, or S. pisciformis) ; the axolotl has a tail fin, 3 pairs of 

 external gills and 4 pairs of open gill clefts, develops sexual organs 

 and lays eggs, it breeds several times a year. The axolotl is found 

 in a state of nature in various parts of Mexico and of the United 

 States. The cavises of this retention of the larval characters and 

 the absence of a metamorphosis from an acjuatic to a land animal 

 appear to be abundance of food and other favourable conditions of 

 life.* Larvae bred irom axolotls in captivity will in some members 

 of the same brood develop into the Amblystoma, in others remain as 

 axolotls. An axolotl, which does not iindergo the metamorphosis 

 naturally, may be made f to undergo it by gradually accustoming 

 it to a terrestrial life, but this becomes increasingly difficult as the 

 animal grows older. Axolotls of six months are comparatively 

 easily induced to metamorphose. Fvirther an animal which has 

 become accustomed to a terrestrial life and has partly luidergone 

 the metamorphosis may be induced to go back to the larval stage. 

 The axolotl becomes sexually mature at about six months. 



Sub-fam. 4. Salamandrinae. Palatal teeth in two longitudinal 

 series, diverging behind, inserted on the inner margin of the two 

 palatine processes, parasphenoid toothless, vertebrae opisthocoelous ; 

 fingers 4, toes 5 except in Salamandrina ; mainly Em-., but found in 

 Algeria, E. Asia, Asia Minor, America. Salamandra Lavir., land- 

 salamanders, tail subcylindrical, Eur., W. Asia ; (S. maculosa Laur., 

 the spotted salamander, eject from the skin glands a poisonous white 

 fluid, viviparous, young are born as larvae from April to June, the eggs 

 then pass into the oviducts and are fertilised before copulation by sper- 



* Gadow, Nature, 67, 1903, p. 330. 



t V. Chauvin, Z. f. w. Z., 21, 1876, and 41, 1885, p. 365. Velasco, 

 Biol. Centralblatt 2, 1882. 



