82 Enamel in the Teeth of an Embryo Edentate 



says that we could adopt Waldeyer's mechanical theory of the enamel 

 pulp as merely serving to make room for the developing tooth, were 

 it not for the fact that the entire enamel organ disappears so early. 

 But I have shown that this is not the case ; the breaking up of the outer 

 epithelial layer and disappearance of the stellate reticulum does not 

 take place any earlier in the armadillo than in other animals. Wliile 

 j-ecognizing the importance of the enamel organ in all animals as direct- 

 ing the growth of the dentine and giving the form to the tooth, I do not 

 believe that the stellate reticulum merely subserves a mechanical func- 

 tioii; but I regard the finding of enamel in the armadillo as strengthen- 

 ing the view that the stellate reticulum holds pabulum for the first layers 

 of enamel. 



I was unable to see Eeinhardt's article, but find through Eose's dis- 

 cussion of it that he describes the rudimentary teeth of Dasypus novem- 

 cinctus as having closed roots and states that they never cut the gum 

 but are later absorbed. He says, however, that the last tooth is sometimes 

 retaino^ in half-grown animals. I did not find the teeth showing any 

 signs of absorption and, as can be seen from Plate II, Fig. 1, they have 

 open roots which are typical of the persistently growing adult teeth. 

 I believe that the teeth will be erupted and thus lost. I am led to this 

 view by the fact that there are indications of the formation of sockets 

 for the last two teeth, and that the teeth are all fairly well developed. 

 Supporting this view, we know that in the Priodontes the teeth in the 

 anterior portion of the Jaw are soon lost and that all traces of the 

 sockets disappear. We also know that in Dasypus seiosus, and the fossil 

 Chlamydotherium, incisors still function. 



While Rose and Ballowitz very correctly state that the discovery of a 

 well developed enamel organ in the armadillos tends to show that they are 

 descended from animals whose teeth are more highly organized, I have 

 shown that enamel is still present on the teeth of the milk dentition, 

 and that the gradual reduction of the enamel, as well as that of the 

 incisor teeth, is still taking place. I believe that older stages of the 

 Dasypus liyhridus, in which, according to Rose, the enamel organ is 

 equally well developed, will show enamel. The question as to whether or 

 not any enamel is present in the tooth-buds of the premanent teeth, and 

 the question as to how long the enamel remains on the milk teeth are 

 matters for further study. The fact that the enamel organ is well 

 developed in the eighth tooth (Plate II, Fig. 6), which has no prede- 

 cessor in the milk dentition, would seem to indicate that this permanent 

 tooth would have enamel. I attempted to demonstrate this by making 

 dry sections of back teeth taken from several adult armadillos; but as 



