184 H. SPENCER HARRISON. 



the first palatine pair, I found a couspiciious longitudinal 

 oval swelling, about 3 by 1 mm., having a whitish appear- 

 ance in the spirit specimen. Closer examination showed 

 that in the anterior portion of this swelling were two small 

 teeth, one oo each side the middle line, and about 1 mm. 

 apart, the left being slightly anterior to the right. Both had 

 their apices directed backwards and inwards, and they had 

 not broken through the oral epithelium. These were, of 

 course, the vomerine teeth, of which the only other indi- 

 cations I have found occurred in a specimen of Stage S (see 

 fig. 13). 



Fig. 24 represents a section passing through the middle of 

 the right vomerine tooth, and through the posterior part of 

 the left. Considering the former, we see that it is a well- 

 developed tooth firmly fused with the underlying bone and 

 showing no signs of degeneration. As regards the left 

 tooth, however, the structure is different. In the figure it 

 appears in two portions, this being due in part to the back- 

 ward curve of the tooth ; but its shape in this section is 

 also influenced by the fact that there is a large aperture 

 on the outer side, through which the surrounding meso- 

 derm is in free communication with the pulp cavity. In 

 other sections, also, the tooth is seen to have a somewhat 

 irregular shape and imperfect construction. These facts 

 point to a condition of degeneracy, and it seems possible 

 that the gap in the dentine ai'ose from a similar imperfection 

 of the enamel organ. I have not found any enamel on either 

 of the teeth, but this may have been entirely removed by 

 decalcification. Siebenrock, who described a specimen with 

 vomerine teeth, stated that the tips were covered with enamel, 

 and this may very well have been the case in the present 

 instance. Reference to fig. 24 will show that there are large 

 ingrowths of epidermis closely applied to the internal faces 

 of the teeth. These are, however, continued anteriorly and 

 posteriorly into more or less glandular structures. How far 

 we should be safe iu assuming the possibility of a tooth 

 change iu this case may be inferred from the previous 



