314 Ileir Paul Frcund on (he Development 



of tlie incmaxilla persists for about as lonf^ as that of the 

 lower jaw. I am at present unable to say anythini^ as to the 

 manner of its disappearance. In embryos with a cephalic 

 length of 1'7 centim., and measuring 4 5 ccntim. in all, the 

 dental fold between the first and second incisors was still 

 present, although it is true that its connexion with the oral 

 epithelium had almost everywhere disappeared. The enamel- 

 organ of i. 2 had become distinctly campanulate. In an older 

 series the dental fold between the two large incisors had 

 already entirely disappeared, although in the model of the 

 stage in question the step u])on the palate was still to be 

 seen, to the anterior margin of which the cord connecting the 

 enamel-organ of t. 2 with the oral cavity was previously 

 attached, while, in all probability as a remnant of this con- 

 nexion, we still find an epithelial projection jutting out 

 slightly into the connective tissue. 



"\Yhile up to this point, with the exception of immaterial 

 modifications, I was able to confirm the statements of Chabry 

 and Pouchet on the subject of the development of the teeth in 

 the rabbit, the results at which I have arrived with reference 

 to the diastema in the upper jaw are quite ditferent from those 

 obtained by the French authors. The latter assert that in 

 the rabbit the dental fold is entirely interrupted in the 

 diastema in both jaws. As I have already mentioned, I can 

 confirm this statement as regards the lower jaw. In the 

 upper jaw, on the contrary, I find the dental fold already 

 typically developed, in the youngest stages investigated by 

 me (measuring about 1 centim. in cephalic length and from 

 2 to 3 centim. in all), throughout the entire length of the 

 diastema between the rudiments of the incisors and those of 

 the molars. A good representation of this is given in fig. 13. 

 The dental fold is situated in precisely the same spot as tiiat 

 in which it is found in mammals with a complete dentition, 

 I. e. internally to the furrow made by the approximately hori- 

 zontal roof of the mouth in bending round into the perpen- 

 dicular mucous membrane of the cheeks. The spot at which 

 the dental told is attached is in the region of the diastema, as 

 in that of the rudiments of the molars, somewhat depressed, 

 towards a protuberance of the surface of the palate situated 

 on the inner side of it (jaw-wall ?). It is perhaps expedient, 

 in addition to the measurements, to give yet other character- 

 istics of the stage in which the fold is found to be fully 

 developed. The stage is that in which the closure of the 

 palate has just been comjileted, in which we still find distinct 

 remains of epithelium in the perpendicular palatal suture, and 

 in which, in the horizontal palatal suture (between the nasal 



