48 CHARLES S. TOMES. 



Although I have examined six or seven specimens, I have 

 not been successful in getting satisfactory sections illus- 

 trating any other stage in the tootli-development. 



I have, however, examined a large number of the teeth 

 of armadillos, removed from the tooth sacs prior to their erup- 

 tion, and have not discovered the least vestige of enamel 

 upon any of them ; the cementum covers them nearly to the 

 tip, but I have never seen it quite reach to the tip of the 

 tooth. 



The results of my inquiries may be summarised thus : 



1. In Tatusia Peba, a creature Avhich has no vestige of 

 enamel upon its teeth, the first histological structure 

 distinctly recognisable in the tooth germ is a well-developed 

 enamel germ, perfectly identical with that seen in other 

 mammalian foetuses of similar age. 



2. That, without any enamel having been formed, and at 

 a very early period in tooth development (namely, contenipo- 

 raneously with the formation of a very thin cap of dentine), 

 this enamel organ assumes a condition precisely similar to 

 that attained to by other enamel organs after their function 

 has been completed by the deposition of the whole thickness 

 of the enamel. 



The persistent connection of the enamel with the oral 

 epithelium from Avhicli it was derived is very well shoAvn by 

 many of the sections, some of Avhich also show well the 

 second inflection of epithelium which forms the enamel germ 

 of the ])ermanent tooth, thus aiFording an additional confir- 

 mation of the fact, to which attention has been drawn by 

 Rapp, Gervais, and Professor Flower, that amongst armadillos 

 Tatusia Peba at all events is not a monophyodont, but pos- 

 sesses two well-developed and functional sets of teeth. 



The occurrence of a structure which is destined to be made 

 no use of in the further course of development would of itself 

 be noteworthy, but this observation on the teeth of the arma- 

 dillo possesses a wider interest, for it bears on the whole 

 question of the affinities and genealogy of that peculiar group, 

 the Edentata ; it would, however, be out of place to enter 

 into a discussion of its probable significance in the pages of a 

 journal specially devoted to Histology ; and, moreover, our 

 knowledge of the development of the teeth of the mammalia 

 being limited to those of a very few species, it would be un- 

 safe to enter upon generalisations built upon so imperfect a 

 basis. 



