408 THE ANIMAL KINGDOM. 



and have been indicated in part above. For details larger works must be 

 consulted. 



The Alpine Triton alpestris, one of the Salamandrina, has been observed 

 to attain sexual maturity, indicated by external signs and by maturation of 

 ova and spermatozoa, at a time when the branchiae are still in functional 

 activity, and the characters of the skeleton show the animal to be really in 

 a larval state. The Axolotl (Siredon pisciformis) has long been known to 

 be competent to sexual functions whilst in a perennibranch condition, a 

 condition in which many individuals remain. Other individuals undergo 

 a change into the Salamandrine Amblystoma mexicanum. This change 

 takes place in its natural habitat, and has been also induced artificially. 



Some Amphibia, but not Anura, show great power of repairing in- 

 juries and of reproducing destroyed or amputated organs. Many of them 

 possess protective coloration which is intensified by the state of distribu- 

 tion of pigment controlled by the nervous system. The Anuran larva feeds 

 on vegetable matters. The adult is carnivorous in all instances, insects, 

 worms, snails, &c., and even higher animals forming the prey. The Am- 

 phibia are absent from nearly all oceanic islands. The Anura are widely dis- 

 tributed : the Urodela are limited to the temperate parts of the northern 

 hemisphere, and are especially numerous in North America. No fossil 

 Gymnophiona are known. Anura and Urodela occur in Miocene strata. 

 The extinct Stegocephali are found in the older Mesozoic strata (Trias) and 

 in the more recent Palaeozoic (Permian, Carboniferous). 



The class Amphibia may be divided into orders as follows : 



I. Gymnophiona. Snake-like in form and subterranean in habit ; no limbs nor 

 tail ; dermic scales imbedded in the integument. Caedlia is found in West Africa, 

 Malabar, and South America ; Siphonops in Brazil and Mexico ; Epicrium in Cey- 

 lon and the Khasya Mountains ; and Rhinatrema, which has no tentaculiferous 

 fossa in Cayenne. There are certain resemblances between this group and the 

 family Aistopoda among Stegocephali; see Fritsch (infra). 



II. Urodela. Body elongated ; as a rule four short extremities and persistent 

 tail with azygos fin. 



1. Ichthyoidea. Eyes small, with or without a circular eyelid-like fold; with 

 biconcave vertebrae and large remnant of notochord. Aquatic in habit. 



(a) Perennibranchiata. Three pairs of persistent gills. Siren, with fore- 

 limbs only, comes from South-east States of North America ; Proteus from caves in 

 Carniola and Dalmatia ; Menobranchus from East States of North America (said to 

 change into Batrachoseps] ; the Axolotl, Siredon, from Central America ; it changes 

 sometimes into Amblystoma Mexicanum. (ft) Derotremata. Gills caducous ; as a 

 rule a persistent gill cleft. Amphiuma (= Muraenopsis] comes from south part of 

 North America ; Menopoma ( = Protonopsis] from Ohio and Alleghany Rivers ; and 

 Sieboldia ( Cryptobranchus) from Japan. 



2. Salamandrina. Branchiae caducous; gill clefts closed in adult; eyelids; 



