DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 469 
18. And as in the latter case, so here, we take these rudi- 
mentary labial outgrowths of epithelial cells to represent the 
abortive enamel-germs of true milk incisors, di4 and di. 
It is, however, when we come to deal with the canine rudi- 
ment in this stage that we really obtain the most emphatic 
testimony to the validity of the interpretation which we have 
given of these interesting vestiges. 
From the fifth incisor the dental lamina, though small, is 
continued back without interruption, and very soon it exhibits 
that great vertical enlargement which we find to be character- 
istic of even the earliest canine rudiments in both upper and 
lower jaws. 
In fig. 21 we show a horizontal section which in front 
passes through the upper part of the fifth incisor mass (28). 
This is seen to bulge out labially (but this is quite above the 
level of rudimentary d=). From the inner or lingual part of 
the Anlage of 22 the dental lamina is continued backwards for 
a short distance, to lose itself, in this sectional plane, in a 
broad area of epithelium (0.e.). This, as may be learnt from 
the drawing, is simply the deep layer of buccal epithelium 
sliced parallel with its free surface. A section or two higher 
this epithelial patch disappears, giving place to the prolonga- 
tion backwards of the narrow dental lamina. Still higher in 
the series the lamina is seen to undergo enlargement so as to 
form the most inferior portion of the canine swelling of the 
lamina (ef. fig. 20). This enlargement markedly increases in 
thickness as it is followed upwards through the horizontal 
series. But although the lamina is so definitely enlarged, the 
differentiation of the permanent tooth has hardly yet set in; 
certainly no distinct outgrowing labial lobe is apparent, like 
that observable in the anterior incisor germs. Itseems highly 
probable, however, that the upper and labially deflected portion 
(marked “c” in fig. 20) of the whole Anlage is really 
equivalent to the labial lobe of the bilobed incisor masses, and 
is thus about to form the labial portion of the cupped enamel- 
organ of the permanent canine. If this be so, then the 
proper morphologically distal margin of the dental lamina is 
