322 riorr Paul Fround on the Development 



certain fH?tance from the epitliclium of tlie upper jaw, and 

 were also frequently continued backwards throutrh a few 

 sections as detached round e]iithelial circles, after which, how- 

 ever, they always came to an end. Tt is very possible that 

 these represent remnants of the dental fold, thoug;h it is true 

 that a more definite proof cannot be advanced. We mi<?ht do 

 this if we could trace such an epithelial cone into continuity 

 eitlier with the dental fold of the incisors in front, or with 

 that of the molars behind. But we can do neither. Yet one 

 argument which supports the idea that these cones are of the 

 nature of a dental fold is to be found in the place from which 

 the ingrowths start, which agrees fairly well with the ty])ical 

 position of the dental fold in Lepus. It is true that in Cavia 

 the relations of the epithelium of the oral cavity and of the 

 mucous membrane of the palate are somewhat different from 

 those in Lepus ; but this is a question which I cannot here 

 proceed to discuss. IMoreover we might establish a proof by 

 the process of exclusion ; besides rudiments of a dental fold, 

 the epithelial cones could only be germs of glands. It is, 

 liowever, improbable that the germs of small oral pituitary 

 glands would be already so distinct in the stage whicli we are 

 considering. But this attempt at a proof is not sufficient. 



Ceicetus frumentarius, Mus musculus, and Mus 



DECUMANUS. 



Few words are needed to dispose of these animals. 

 Although we had at our disposal continuous series of at least 

 the two last-named species, the investigation of them never- 

 theless produced absolutely negative results. Not a trace of 

 rudimentary tooth-germs was found either in the neighbour- 

 hood of the incisors or in the diastema. 



The discussion and valuation of my results may be divided 

 into heads according to the questions with which we 

 started : — 



(1) Are embryonic tooth-rudiments found in the neighbour- 

 hood of the incisors in Rodents ? To this we reply : — In 

 Lepus we find a rudimentary tooth in the upper and lower 

 jaw in front of the large incisor, as already discovered by 

 Chabry and Pouchet. This remarkable observation appears 

 to have escaped the notice of most of the subsequent authors, 

 but I was able to confirm it and to add that evidently the 

 same tooth-rudiment is also present in the squirrel. 



Now Dr. Fleischmann has led me to inquire whether this 

 rudimentary tooth represents the remnant of an 1. 1 — in whicli 

 case the large incisor would have to be designated /. 2, which 



