288 THE HISTORY OF CREATION. 



into the cavity of the mouth) into air passages. The series 

 of the ancestors of man which breathed air through lungs 

 began at this stage. Their organisation may probably in 

 many respects have agreed with that of the still living 

 Ceratodus and Protopterus, but at the same time may 

 have been very different. They probably lived at the 

 beginning of the Devonian period. Their existence is 

 proved by comparative anatomy, which shows the Dipneusta 

 to be an intermediate stage between the Selachii and 

 Amphibia. 



Thirteenth Stage : Gilled Amphibians (Sozobranchia) . 



Out of those Mud Fish, which we considered the primary 

 forms of all the Vertebrata which breathe through lungs, 

 there developed the class of Amphibia as the main line 

 (pp. 205, 216). Here began the five-toed formation of the 

 foot (the Pentadactyla), which was thence transmitted to 

 the higher Vertebrata, and finally also to Man. The gilled 

 Amphibians must be looked upon as our most ancient 

 ancestors of the class of Amphibia; besides possessing 

 luncs they retained throughout life regular gills, like the 

 still living Proteus and Axolotl (p. 218). They originated 

 out of the Dipneusta by the transformation of the paddling 

 fins into five-toed legs, and also by the more perfect dif- 

 ferentiation of various organs, especially of the vertebral 

 column. In any case they existed about the middle of the 

 palaeolithic, or primary period, possibly even before the Coal 

 period ; for fossil Amphibia are found in coal. The proof 

 that similar giUed Amphibians were our direct ancestors, is 

 given by the comparative anatomy and the ontogeny of 

 Amphibia and Mammals. 



