478 J. LT. WILSON AND J. P. HILL. 
just become recognisable as a distinct Anlage, though dp2 was 
already a cup-like enamel-organ. 
Figs. 28 and 29 represent coronal sections through m4, 
rather behind the middle of the tooth, and through the 
posterior part of the tooth, respectively. In these the process 
of differentiation of the tooth Anlage from the parent lamina 
is seen to be well advanced, so that the residual dental lamina 
(rdl). which remains, after separation from it of a tooth 
rudiment, appears with its free distal margin or fundus some- 
what swollen, and freely projecting by the side of the first 
molar Anlage. 
As the residual lamina is traced backwards from the region 
of m+ (ef. figs. 25 and 26) it retains for a time on its labial 
face some irregular projections over the area corresponding to 
that occupied further forwards by the differentiated enamel- 
organ of m1. A comparison of figs. 29 and 30 (the latter 
being the tenth section behind the former) will serve to 
explain this statement. It will also appear that the residual 
dental lamina of the first molar region has very slightly 
increased in thickness. Here, of course, it simply constitutes 
the primitive and undifferentiated lamina intermediate between 
the region of the first and second molars. 
Fig. 31, taken some little distance further back, shows con- 
siderable broadening of the lamina at its free margin, after 
somewhat the same fashion as we have seen to characterise the 
Anlage of the first molar in the preceding Stage 11. 
Here, again, the thickening of the fundus appears to be 
chiefly due to a proliferation of the cells at the labial lip of the 
free margin of the lamina. 
Fig. 32 shows a section immediately in front of the plane at 
which the molar lamina abruptly terminates. 
In the last three sections (cf. especially figs. 80 and 31) the 
prominent labially directed process (/.0.) near the base or 
attached margin of the dental lamina is the cross-section of a 
continuous secondary lamina in this region (m+ to m2), 
whose significance will be discussed below in connection with 
the questions of molar homology (vide Part II). 
