84: GENERAL EVOLUTION. 



the ossified anJ non-ossified types of Chelonia occurs during tlie 

 life of the individuals of tlie genus Dermatemys. 



But, in attempting to demonstrate this proposition, we must 

 bring forward facts of another kind. The anti-developmentalists 

 are accustomed to jjut such changes aside, as part of the necessary 

 history of established types ; hence we will not appeal to such. 



1. The frog Ranula affinis, of South America, was described 

 by Peters as probably a climatal variety of European Rana tempo- 

 raria. In this he is supported by the fact that the specific char- 

 acters do not differ more than would characterize it as a local 

 variety, were it an inhabitant of Europe. But I have found that 

 it differs generically in tlie non-ossification of tlie ethmoid bone, 

 as has been confirmed by Steindachner, and rej)resents an embry- 

 onic condition of the same bone in Eana. It is in fact an unde- 

 veloped Rana. That this is a true genus is confirmed by many 

 specimens, by additional species, and by the fact that the allied 

 genus Trypheropsis, embracing three sjiecies in the same region, 

 differs in the same way from the otherwise identical genus of the 

 Old World, Hylorana. 



2. The South African Saurians, Gliammmura anguina and 

 Mancus macrolepis, are very closely allied in specific characters in 

 all respects, though distinct. They have one imj^ortant ground 

 of generic distinction : the latter has one pair of limbs less than 

 the former. They are rudimental in Chamsesaura, and the disap- 

 pearance in Mancus is but another step in the same direction. 

 The difference in specific characters is of much less degree. 



3. In the genus Celestus there are numerous species, which 

 range from a slender snake-like form with weak limbs, to stouter, 

 strong-limbed forms with a more saurian build. Among these 

 the Haytian G. plioxinus is well distinguished by form and color- 

 ation. An allied genus from the same region is Panolopus, which 

 in specific characters approaches the C. pJioxinus very closely, 

 much more so than any Celestus (one species possibly excepted). 

 But in generic characters it is distinguished by the loss of all its 

 toes and the non-separation of nine plates on the end of the muz- 

 zle. The genus Diploglossus, on the other hand, occupying a 

 superior place on account of the division of the fronto-nasal into 

 three, is, in specific characters (of D, monotropis) much closer to 

 the stout Celesti than the species of the latter genus are among 

 themselves. 



4. The Gronias nigrilalris is a Silurid, which in specific char- 



