576 Studies in the Theory of Descent. 



skin-like appendages (Kolliker), or more precisely, 

 the half webs which connect the proximal ex- 

 tremities of the toes on all the feet (Weismann). 



7. The teeth are disposed in this species, as in 

 all other Amblystomce, in transverse series ; whilst 

 in Axolotl, as in Triton larvae, they are arranged 

 at the sides of the jaw in the form of a curved 

 arch-like band beset with several rows of teeth. H 

 (Dumeril. See his fig., loc. cit, p. 279). 



8. In Axolotl the lower jaw, in addition to the 

 teeth on the upper edge of the bone, also bears 

 " de tres petites dents disposees sur plusieurs 

 rangs;" these last disappear after metamorphosis 

 (Dumeril). I will add that the persistent teeth 

 belong to the os dentale of the lower jaw, and 

 those that are shed to the os operculare 



9. The surface of the posterior moveable part 

 of the body is slightly concave both before and 

 after transformation ; the anterior part is, how- 



14 Dumeril represents the teeth of the vomer as separated 

 from those of the os palatinum by a gap. This is probably 

 accidental, since Gegenbaur (Friedrich u. Gegenbaur, the skull 

 of Axolotl, Wiirzburg, 1849) figures the rows of teeth as 

 passing over from the one bone to the other without interrup- 

 tion. This was the case with the Axolotls which I have been 

 able to examine on this point ; but this small discrepancy is, 

 however, quite immaterial to the question here under con- 

 sideration. 



11 See O. Hertwig " Uber das Zahnsystem der Amphibien 

 und seine Bedeutung fur die Genese des Skelets der Mund- 

 hohle." Archiv. fur microsc. Anat., vol. xi. Supplement, 

 1874. 



