508 J. ‘I. WILSON AND J. P. HILL. 
Lower Jaw.—The dental lamina begins only a very short 
distance in front of the anterior plane of 7;, so that the ante- 
rior segment of the dental lamina referred to in the preceding 
stages is greatly foreshortened. 
Fig. 65 represents a coronal section passing through the 
dental lamina which just shaves the forwardly directed apical 
part of the first incisor. The dental lamina in this situation 
now shows a fairly well differentiated epithelial enamel-germ 
(7. e.0.), which we are inclined to interpret as that of a lost 
incisor in front of 7;. The facts relating to this important 
structure are deserving of very careful attention, and are as 
follows: 
During the period which elapses between Stage 111 on the 
one hand and Stages v and vi on the other, the dental lamina 
in front of <; appears to undergo an elongation from behind 
forwards. This anterior segment of the lamina exhibits, in 
Stages v and vi, a very well-marked thickening, which de- 
creases posteriorly where it is continuous with the residual 
lamina of 7;. 
In Stage vir the anterior growth of the large 77 has 
encroached upon the region in question, and accordingly the 
latter portion of the dental lamina is both relatively and ab- 
solutely shorter, antero-posteriorly, than it was in the imme- 
diately preceding stages. At the same time, however, it has 
become much more definitely thickened, and now seems to form 
the rudiment of a distinct enamel-organ with a flattened or 
slightly concave base (fig. 65). 
This enamel-organ now appears as if formed by the most 
anterior extremity of the residual dental lamina of iz. At this 
stage posterior sections of the rudiment in question would 
certainly suggest the idea that it is related successionally to 7;. 
But a consideration of the antecedent conditions of this struc- 
ture, arising as it does entirely independently of and quite in 
front of 7;, seems to us sufficient to dispose of such an inter- 
pretation in view of the very ample grounds, both general and 
special, for maintaining the truly successional nature of i; 
