30G CLASS AMPHIBIA. 



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

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

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

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

 Hayti (1 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. lugubris 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 transverse 

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

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

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

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

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

 Batrachypertis 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. persimile) 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 formerly thought to be an adult form and called Siredon 

 (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 causes of this retention of the larval characters and 

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

 appear to be abundance of food and other favourable conditions of 

 life.* Larvae bred from 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 undergo the metamorphosis 

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

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

 animal grows older. Axolotls of six months are comparatively 

 easily induced to metamorphose. Fiirther an animal which has 

 become accustomed to a terrestrial life and has partly undergone 

 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 Eur., but found in 

 Algeria, E. Asia, Asia Minor, America. Salamandra Laur., 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. /. w. Z., 27, 1876, and 41, 1885, p. 365. Velasco, 

 Biol. Centralblatt 2, 1882. 



