310 Herr Paul Freund on the Development 



thelium. In short, apart from the absence of enamel, it is a 

 thoroughly typical representation of a small tooth-rudiment, 

 such as we are otherwise wont to find in lower Vertebrates. 

 The connective cord, wliich unites the enamel-organ of the 

 rudimentary tooth with the epithelium of the oral cavity, 

 actually extends with its anterior end, as stated by the French 

 authors, as far as the posterior circumference of the mur plon- 

 geant^ which is here but little developed. Further back- 

 wards, however, this connective cord proceeds, as is shown in 

 fig, 1, from the unthickened epithelium of the oral cavity. 

 Moreover, we see from the figure that a strong epithelial pro- 

 jection, which is directed inwards, starts from the spot where 

 the connective cord passes into the actual enamel-bell 

 (Schmelzglocke). This arrangement is repeated more or less 

 decidedly in each section. According to the customary con- 

 ception the tract a-/3 in fig. 1 would have to be regarded as 

 the " dental fold " ('' Zahnleiste "), on the outer side of which, 

 close above the end without a neck, the enamel-organ of the 

 rudimentary tooth would be situated. Whether this mode of 

 interpretation is here correct, can only be determined by the 

 study of younger stages, which I am reserving to myself. 

 Now the enamel-organ of the large incisor of the lower jaw is 

 directly connected with the posterior side of the enamel-organ 

 of the rudimentary tooth ; in the same manner the cord which 

 connects the enamel-organ of the rudimentary tooth with the 

 epithelium of the oral cavity is posteriorly prolonged directly 

 into the similar connective cord of the enamel-organ of the 

 large incisor. If, as has been indicated above, we regard 

 this cord as a dental fold, this continuity of the dental fold 

 from one enamel-organ to the other would be nothing unusual, 

 — on the contrary, it is in accordance with the general rule. 

 The direct connexion, however, of two enamel-organs, as, 

 moreover, also shown with great distinctness in fig. 19 (longi- 

 tudinal section) of Pouchet and Chabry, is unusual. The 

 enamel-organ of the permanent incisor is still at a very low 

 stage of development. It is a lumpy epithelial mass, which 

 on the posterior side appears somewhat flattened and indented. 

 This shallow hollow subsequently deepens into the bell of the 

 enamel-organ, which is open towards the rear. In the rudi- 

 ment of the large incisor no trace of tooth-substance is yet 

 developed. 



Behind the large incisor the dental fold in the lower jaw 

 entirely ceases. In order to dispose of this question at once, 

 it may be mentioned that in the case of Lepus^ in this, as in 

 all subsequent stages, an absolute diastema is found in the 



