DISTRIBUTION OF ORGANISMS. 199 



The reduction of limbs in some of these latter species re- 

 minds us of the lacertilian animals on the approach of that 

 family to the serpent form. It is not, therefore, surprising to 

 learn that there is a genus of undoubted batrachians which 

 are wholly serpentine in figure, that is, without limbs, and also 

 possessed, like the serpents, of unequal lungs. These are the 

 Cecilia, or blind-worm, and kindred species, all of them in- 

 habitants of warm countries ; usually of a very attenuated 

 form, and about two feet long. Till lately, the cecilia was 

 ranked with serpents ; but its passing through a metamor- 

 phosis, united to a consideration of its naked skin, has at 

 length assigned it to the present order. Vegetable matters, 

 as well as mud and sand, have been found in the stomachs of 

 the ceciliadae. 



The batrachia have a particular value on the present occa- 

 sion, as, although probably but the relics of an order once 

 containing many more genera, and some of these much larger 

 in bulk, they present unequivocal affinities to the grade below 

 them, and also striking affinities amongst themselves, while 

 their reproduction supplies a faithful picture of the principal 

 phenomenon concerned in the development theory. Several 

 genera, by retaining portions of the fish character, make the 

 descent of the whole from fishes still more apparent. Pro- 

 fessor Owen has shown that not merely in the retention of 

 gills, but in peculiarities of teeth, can the nearness of some of 

 the batrachia to fishes be distinguished. The Ranidae appear 

 to compose two kindred lines ; the toads, in their more ter- 

 restrial habits, may be said to make a greater advance than 

 the frogs. In the Salamandridae, there are also traces of at 

 least two lines : amongst them, from smooth skins, and aquatic 

 habits, to tuberculated skins and land habits, we pass through 

 a well-knit chain of affinities. In the other Batrachia, we see 

 only detached developments from the neighbouring fish-form, 

 which we may suppose, in some instances at least, to have 

 been prevented from advancing into new forms by the circum- 

 stances in which they are placed. 



With this account of the Reptiles, the geological history of 

 the class, as far as it goes, appears in harmony. First, it is 

 after fish that reptiles occur in time, as it is after fish that 

 they stand in organization. Early in the Carbonigenous era, 

 after fishes had existed for the space of two entire formations, 

 there arises a family assuming a trace of reptilian character, in 

 an inner row of Saurian teeth. The Sauroid fishes, as they 



