PROGENITOES OF MAN. 289 



FotTETEENTH Stage : Tailed Amphibians (Sozura). 



Our amphibious ancestors which retained their gills 

 throughout life, were replaced at a later period by other 

 Amphibia, which, by metamorphosis, lost the gills which 

 they had possessed in early life, but retained the tail, as in 

 the case of the salamanders and newts of the present day. 

 (Compare p. 218.) They originated out of the gilled 

 Amphibians by accustoming themselves in early life to 

 breathe only through gills, and later in life only through 

 lungs. They probably existed even in the second half 

 of the primary, namely, during the Permian period, but 

 possibly even during the Coal period. The proof of their 

 existence lies in the fact that tailed Amphibians form a 

 necessary intermediate link between the preceding and 

 succeeding stages. 



Fifteenth Stage : PrimaBval Amniota (Protamnia). 



The name Protamnion we have given to the primary 

 form of the three higher classes of Vertebrate animals, 

 out of which the Proreptilia and the Promammalia developed 

 as two diverging branches (p. 222). It originated out 

 of unknown tailed Amphibia by the complete loss of the 

 gills, by the formation of the amnion, of the cochlea, and 

 of the round window in the auditory organ, and of the 

 organs of tears. It probably originated in the beginning 

 of the mesoKthic or secondary period, perhaps even towards 

 the end of the primary, in the Permian period. The 

 certain proof that it once existed lies in the comparative 

 anatomy and the ontogeny of the Amniota ; for all Reptiles, 

 Birds, and Mammals, including Man, agree in so many 

 important characteristics that they must, with fuU assur- 



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