374 THE AMERICAN NATURALIST [Vol. XLIV 



The modern amphibia present many problems for 

 consideration. Among the most interesting of these is 

 the one which is concerned with the phylogeny of the 

 living forms. An attempt lias previously been made 

 by the writer 1 to elucidate the problem of descent so far 

 as the Caudata are concerned. The present contribution 

 is a further extension of that effort and it supports the 

 conclusions there drawn. 



Eepresentatives of several genera of the modern 

 Caudata have been dissected in order to make a direct 

 comparison of the fossil alimentary canal with that of 

 the recent forms. Among the forms dissected may be 

 mentioned Ambystoma tigrinum, Ambif stoma opacum, 

 Diem gei gins torosns, Diem get gins vi rideseens, Desmog- 

 nathus fuscus Kaf., Spelerpes bUmeatus Green, etc. In 

 some cases representatives of several stages in the growth 

 of the individual species have been available for study. 

 The alimentary tract of Desmognathus fuscus Kaf. from 

 the vicinity of Ithaca, New York, resembles in a marked 

 degree that of the fossil form. The nearest approach to 

 the condition there represented is, however, found in an 

 immature branchiate individual of some 47 millimeters 

 in length, of Dion get gins forosns Kscli., from a fresh- 

 water pond on Orcas Island in Puget Sound. The pres- 

 ence of this species on the island is very suggestive and 

 its bearing on the geological age of the caudate amphibia 

 will be given elsewhere. It is of extreme interest that 

 the condition represented by the fossil should resemble 

 so closely that of an immature rather than a mature 

 form since it lends support to the recapitulation theory. 

 Perhaps the representative species of the genera Des- 

 mognatlius, Spelerpes, Hemidaetglus, etc., are forms 

 which have become restricted in their development and 

 thus represent more nearly in the structure of their 

 mentary canal the ancestral condition, as is also the 

 in the immature form of the Diem get gins torosus E 



The writer has attempted to show that the modern 



1 American Naturalist, XLII, No. 498, June, 1908. 



