DISTRIBUTION OF ORGANISMS. 177 



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 ap- 

 parent. Professor 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 terrestrial habits, may be said to make a greater 

 advance than the frogs. In the Salamandridse, 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 circumstances 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 an entire formation, 

 there arises a family assuming a trace of reptilian character, 

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

 they are called, increase and multiply, and, several ages 

 thereafter, in the Muschelkalk, the Enaliosauria, or fish- 

 crocodiles (ichthyosaur, etc.), are presented, in which the 

 passage to the reptile is clear and distinct. Before this event 

 in the saurian line, a similar and more effectual transition 

 had taken place in at least two other animal series, resulting 



