THE POSITION OF THE CLASS AMPHIBIA IN THE PHYLUM VERTEBRATA.–There is no doubt that the Amphibia have sprung from fish-like ancestors, and that they in turn have given rise to the Reptilia. The Amphibia consequently hold a very important intermediate position. It was perhaps not a fortunate innovation when Huxley brigaded them with the Fishes as _Ichthyopsida_, thereby separating them more from the _Sauropsida_ (= Reptilia and Aves), than is justifiable,–perhaps more than he himself intended. The connecting-link, in any case, is formed by the Stegocephali; all the 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 Reptiles, notably to such Proreptilia as _Eryops_ and _Cricotus_, and even to the Lepospondylous Prosauria, is extremely gradual, and the steps are almost imperceptible. Naturally, {6}assuming evolution to be true, there must have lived countless creatures which were a "rudis indigestaque moles," neither Amphibia nor Reptilia, in the present intensified sense of the systematist. The same consideration applies equally to the line which leads downwards to the Fishes. But the great gulf within the Vertebrata lies between Fishes and Amphibia, between absolutely aquatic creatures with internal gills and "fins," and terrestrial, tetrapodous creatures, with lungs and fingers and toes. On the side of the fishes only the Dipnoi and the Crossopterygii come into consideration.