Characteristics of the Vertebrata. Ixvii 



tremata, and more or fewer of the cartilaginous branchial arches 

 disappear after the disappearance of the branchiae they carried. 



The Alpine Triton, one of the Caducibranchiate Amphibia, has 

 been observed to attain sexual maturity as indicated not only by 

 external characteristics, but by the maturation of ova and sperma- 

 tozoa, at a time when the branchiae were still in functional activity, 

 and when the characters of the bones in the roof of the mouth, and 

 the presence of a continuous non-constricted cylindriform chorda 

 dorsalis, showed the animal to be really in a larval state. The 

 Axolotl [Slredou pisciformh) has long- been known to be competent 

 to sexual functions, whilst organs, regarded as provisional in other 

 Amphibia, were still persistent ; and it has consequently been 

 classed with the Perennibrayichiata until recently, when it was 

 discovered that its gills are really deciduous, though at varying 

 periods in the life of the animal. Similar instances of larval 

 Ichthyoids maturing sexual products are furnished to us by the 

 immature Lamprey, and the young male Salmon, known as the 

 ' parr.' Some Amphibia possess a great power of repairing injuries, 

 and of reproducing destroyed or amputated organs. It has been 

 stated, however, that it is necessary for svich reproduction that the 

 basal or some other portion of the mutilated organ or limb should 

 be left in situ; and it is not certain that the Urodela with well- 

 developed lungs, such as Salamandra terrestris, and the Anura 

 generally, possess this power in their adult state, at least to the 

 same extent as they do when larvae, or to the same extent as 

 other Amphibia in which the organs for aerial respiration are 

 less highly evolved. 



The Amphibia are placed together with the class Pisces in a 

 single group, the Ichthjjops'ida^ s. Aiiamniota. It is with the more 

 generalized forms of that class, viz., the Ganoidei and the Dijmoi, 

 rather than with those which, as the Teleostei, combine in this 

 organization the largest number of specially piscine characteristics, 

 that the Amphibia are allied. The Dipnoi indeed have been ranked 

 as a separate order of Amphibia, under the title ' Ichthyobatrachia,' 

 though, if we have regard to the entirety of their organism, we 

 are compelled to regard them as true Fish. The Elasmobranchii 

 resemble certain of the Amphibia in developing external gills in 

 embryonic life, and they were spoken of by Linnaeus as AnqMhia 

 nantia. The absence, however, in them of any save an occasional 



e Q, 



