DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 567 
epithelium as is the dental lamina in the antemolar region. 
That this is the case as far as the entire molar lamina in Stage 11 
is concerned we have already pointed out, but we may here 
at once state that we have observed the extension backwards 
of the dental lamina in continuity with the oral epithelium in 
other stages as far as the region of the third molar inclusive 
in the upper jaw, and just short of this region in the lower. 
In fact, it may be stated that this continuity with the oral 
epithelium exists just as far back as the oral epithelium 
overlies the molar Anlagen. The most posterior molars 
appear to originate precociously from a backward free pro- 
longation of the lamina before the lengthening of the jaw 
permits a co-extensive prolongation backwards of the oral epi- 
thelium. 
In pig embryos of 20 mm. head-length, we also find the 
connection of the dental lamina with the oral epithelium 
maintained right up to the hinder end of the molar region, or 
within a couple of sections of it. 
We are, therefore, little surprised to find that in the pig the 
labio-dental or labio-alveolar lamina (i. e. the epithelial Anlage 
of the lip-furrow which is formed anteriorly) is continued back 
into the molar region as the Anlage of what we may here call 
the gum-cheek-furrow. And at the extreme posterior end of 
the proper dental lamina the latter is seen to be fused near its 
basal or attached margin with the labio-alveolar lamina, the 
two structures forming parts of acommon Anlage, as Rése has 
shown to be the case at first in the anterior region of the jaw. 
Fig. 83 illustrates the condition met with close to the pos- 
terior end of the molar lamina in the upper jaw of such a pig 
embryo. The lamina stops rather abruptly a few sections 
further back. 
The section figured passes close behind the posterior end of 
the molar Anlage,—in fact, partly shavesit. Projecting labially 
from the neck of the lamina near the oral epithelium there is 
seen in cross-section a laminar projection (d.0.) of the kind 
whose significance we are discussing, and which is proved, by 
examination of the series, to be neither more nor less than a 
