PARALLELISM. 199 



all the characters possessed by the genera Hylella 

 and Hyla, either at or just before the mature state of 

 the latter, as the ethmoid bone is not always ossified 

 in advance of the parietals. It soon, however, becomes 

 a Scytopis, next an Osteocephalus, and finally a Tra- 

 chycephalus. It belongs successively to these genera, 

 for an exhaustive anatomical examination has failed 

 to reveal any characters by which, during these stages, 

 it could be distinguished from these genera. The same 

 succession in development of the genera of the other 

 families is well known, the genus Otaspis of the Bu- 

 fonidae attaining a point beyond any of the others, in 

 the enclosure of its membranum tympani posteriorly 

 by dermoossification. 



Finally reaching in our review the relations of spe- 

 cific characters, the readers will call to mind that the 

 species of the lacertilian genus Cnemidophorus (page 

 41) are either striped, spotted, or cross-banded, and 

 that the Lacerta muralis agrees with them in this re- 

 spect. It was also shown that the young of all the 

 species are striped, and that the cross-banded forms 

 pass through not only a striped, but an intermediate 

 spotted stage, before attaining the adult coloration. 



The young of spotted salamanders are without 

 spots (genera Amblystoma and Salamandra e g.) ; so 

 that unspotted species resemble the young of the 

 spotted. In many species of birds of more or less uni- 

 form patterns of coloration, the young are spotted. In 

 some of these the females remain spotted throughout 

 adult life. In some other species both sexes retain 

 the spotted coloration of the young. The young of 

 most deer are spotted. In the fallow-deer (Axis) the 

 adults retain the spotted coloration, thus resembling 

 the young of most of the species. 



