CHARACTERS AND J'OSITIOX 5 



Numbers 1 (6), 1 (c), 2, 3, 4 and 1 -1 separate tlie Amphibia iVom tlie Fishes. 



Numbeis 1, 6 ft), 7, 8, 9, 11, 13, in separate them from the Reptiles, 

 Birds, and ^lammals. 



Number 2 separates tliem from tlie Fislies, Reptiles, and Hi ids. 



Number 5 sejjarates tliem from the Mammals. 



Number 6 («) separates them from tlie Fishes (exel. l)ipn(H„ Birds and 

 Mammals. 



We can, therefore, very easily detiiie all tlie Ainpliil.ia, Ijoth 

 recent and extinct, l»y a combination of the cliaracters enumerated 

 above. For instance, by the combination of numliers 2, ;'> or 4 

 with either 7, 8, 9, 11, \?> or 1.5. 



Ampliicondylous Anamnia would be an absolutely correct and 

 all-sufficient diagnosis, but it would be of little use in the deter- 

 mination of adult specimens ; and the tetrapodous character is of 

 no avail for Apoda. AmpJiicondylous animals irit/iout an intra - 

 cranial hypo(jloss(d nerve is a more practical diagnosis. 



In the case of living Urodela and Anura the absence of any 

 scales in the skin affords a more popular character ; it is unfor- 

 tunately not applicable to the Apoda, many of wiiich possess 

 dermal scales, although these are liidden in the imbricating 

 transverse rings of the epidermis ; and the frequent occurrence o\ 

 typical scales of both ecto- and meso-dermal composition in many 

 of the Stegocephali forces us to discard the scales, or rather their 

 absence, as a diagnostic character of the class Amphibia. 'J'he 

 same applies to the mostly soft, moist, or clammy, and a cry glan- 

 dular nature of the skin. 



The position of the class Amphibia in the Phylum Verte- 

 brata. — There is no doubt that the Amphibia have sprung I'rom 

 fish-like ancestors, and that they in turn have given rise to tlie 

 Eeptilia. Tlie Amphibia consequently hold a Aery important 

 intermediate position. It was perhaps not a fortunate innova- 

 tion when Huxley brigaded them with the Fishes as Ichtliyopsida, 

 thereby separating them more from the SaurojJsida ( = lke])tilia 

 and Aves), than is justiiialjle, — perhaps more than he himself 

 intended. The connecting-link, in any case, is formed by the 

 Stegocephali ; all tlie recent Orders, the Apoda, Urodela, and 

 Anura, are far too specialised to have any claims to the direct 

 ancestral connections. The line leading from Stegocephali to 

 fossil Eeptiles, notably to such Proreptilia as Eryops and 

 Cricotus, and even to the Lepospondylous I*rosauria, is extremely 

 gradual, and tlie steps are almost imperceptible. Natunilly, 



