The piscine descent of the Amphibia is still proclaimed by the following features.–(1) The possession by the heart of a long conus arteriosus, provided with, in many cases, numerous valves, or at least (Anura) one series at the base, another at the beginning of the truncus where the arterial arches branch off; (2) the strictly symmetrical arrangement of these arches; (3) the trilocular heart is still like that of the Lung-fishes or Dipnoi; (4) the occurrence of as many as four or even five branchial skeletal arches in the larval stage; (5) the glottis is supported by cartilages which themselves are derivatives of posterior visceral arches; (6) the development of the vertebrae (Stegocephali and Urodela) from four pairs of arcualia, and the formation of the intervertebral joints by a split across the intervertebral ring of cartilage: this feature is unknown in Reptilia, but it occurs also in _Lepidosteus_, most probably also in _Polypterus_; (7) the hypoglossal still retains the character of a post-cranial or cervical spinal nerve; (8) the presence of lateral sense-organs; (9) the possession of external gills is of somewhat doubtful phylogenetic value, although such gills occur amongst fishes only in Dipnoi and Crossopterygii. It is not unlikely that in the Amphibia these organs owe their origin to entirely larval requirements, while the suctorial mouth of the larvae of the Anura and many fishes has certainly no ancestral meaning, but is a case of convergent development. The usual diagnoses of the Amphibia contain the statement that they, or most of them, undergo a metamorphosis, or pass through a larval stage. The same applies to various fishes; while, on the other hand, the larval (not ancestral) stage has become permanent in the Proteidae and Sirenidae; and lastly, we cannot well speak of larvae in the viviparous _Salamandra atra_. {7}THE EVOLUTION OF AN ADEQUATE CLASSIFICATION OF THE AMPHIBIA has been a long process. Even their recognition as a class, separate from, and of equal rank with that of, the Reptilia, was by no means generally accepted until comparatively recent times. A historical sketch of the laborious, often painful, striving for light, in France and Germany, then in England, and lastly in America, is not without interest. The term _Amphibia_ was invented by Linnaeus for the third class of animals in his famous "Systema Naturae." It comprises a very queer assembly, which, even in the 13th edition (1767), stands as follows:– 1. REPTILES PEDATI, with the four "genera" _Testudo_, _Draco_, _Lacerta_, and _Rana_. _Lacerta_ includes Crocodiles, Lizards, and Newts! 2. SERPENTES APODES. 3. NANTES PINNATI. Elasmobranchs, Sturgeons, Lampreys, and various other fishes. Laurenti, 1768, in a dissertation entitled "Specimen medicum, exhibens Synopsin Reptilium ...," uses Brisson's term, REPTILES, and divides them into:– REPTILIA SALIENTIA, these are the Anura.