498 J. T. WILSON AND J. BP. HILL. 
that it is related more intimately to 7, than to 7,, as might be 
suggested by fig. 57. We can only interpret this as a vestige 
of a diz, of which a trace was found in Stage 111 in the form 
of a flattened mass of epithelial cells labially to the Anlage 
of 73. 
As iz and is disappear posteriorly, the dental lamina is 
greatly reduced in depth for some distance, and then gradually 
deepens again, becoming more and more elongated and swollen 
as the canine region is approached. Here (fig. 58), but still 
some distance in front of the actual canine enamel-organ, we 
find the vestigial d; attached to the lamina by a delicate epi- 
thelial strand (cd.). 
It is of interest to note that in one of our series of sections 
of this stage this is a precociously calcified tooth lke di; 
(fig. 58), while in another series it exists in the form only of 
a loose and degenerating epithelial mass. 
The identification of this vestigial tooth as d; is rendered 
easy by a comparison of its relations in the earlier stages 
where no possible doubt could be felt, and where its present 
relative dislocation is evidently in progress. 
The lower permanent canine has not progressed very rapidly 
during the period intervening between Stages 111 and Iv. 
Although it has attained considerable dimensions, its papilla is 
still very rudimentary, and its enamel-organ is only slightly 
cupped. Furthermore it is not yet differentiated off from the 
lamina, so that the residual lamina has not yet come into 
existence. Only a short stretch of lamina intervenes between 
the last trace of the canine and the commencement of the 
first premolar (p;). The latter tooth is more advanced in 
development than the canine, though not greatly so. It is 
deeply cupped by a prominent papilla, and the differentiation 
of the residual dental lamina has begun. 
The second premolar is in a precisely similar condition to 
that of the first, tapering away at its posterior end into a fairly 
deep and thick dental lamina, which is continued back into the 
third premolar region. In this situation dp; comes into view, 
placed away to the labial side of the lamina. Since the 
