GENESIS OF MAN. 5 1 



therefore employed their gills, which they retained, when in the 

 water, but breathed through their lungs when on land. They form, 

 therefore, a very anomalous and interesting transition group, con- 

 necting the lowest fishes with the lowest amphibians. They were 

 a very large class in paleolithic time, as their dental remains tes- 

 tify, but at present only three genera are known, each with a single 

 species, viz : — Protopterus annectens, of the rivers of Africa ; Lepi- 

 dosiren paradoxa, of tropical America ; and Ceratodus Forsteri, from 

 South Australian swamps. 



Gegenbaur has demonstrated that the real character of the fins 

 of fishes is that of many-toed feet. The changes that led from the 

 fish to the Dipneusta seem not to have affected the number of these 

 toes, although a certain adaptation of the fins to terrestial locomo- 

 tion was perceptible. The next important transformation was to 

 concern this part of the animal anatomy. The animals nearest 

 related to the Dipneusta are unquestionably the amphibians, with 

 which the former are frequently classed; but they differ from them 

 in the important respect of possessing regular, five-toed feet. But 

 one conclusion can be drawn from this fact, and this is that among 

 the many and varied forms of the once great Dipneusta class, there 

 was one whose locomotive organs had become transformed through 

 adaptation and natural selection into five-toed feet, and that from 

 this long extinct five-toed progenitor, the present amphibians have 

 descended. The human embryo itself, and that of all the higher 

 vertebrates, pass through an analogous transition. 



With frogs, toads, and other higher amphibians, as we are most 

 familiar with them, the anthropogenetic line has no direct connec- 

 tion. It constantly hugs the base of the whole group, exhibiting 

 direct relationships only with the Sozobranchia, which, therefore, 

 form the thirteenth, and the Sozura, which form the fourteenth 

 stage. 



The former of these sub-classes comprises the Proteus, the Siren, 

 and the Siredon, as among its best-known representatives, while to 

 the latter belong the Triton and the Salamander. These once 

 abundant but now comparatively rare creatures have furnished 

 naturalists with some of the most interesting examples of what 

 may almost be called the visible transmutation of species. It is 

 well known that frogs and toads (Anura), the more highly differ- 

 entiated amphibians, instead of possessing both lungs and gills 



