DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 481 
segment of the dental lamina as éz, and is therefore related to 
it as belonging to a labial or elder generation. Its superficial 
position would almost seem to lend support to this view. But 
it is absolutely negatived by the facts elicited by more careful 
study. The true explanation was arrived at by following the 
dental lamina forwards and backwards in the coronal series, 
by careful collation with the appearances seen in the corre- 
sponding locality in coronal series in Stage 11, and above all 
with those found in the examination of horizontal sections of 
Stage 111 itself. By means of such observations we have 
been able to determine with certainty that the longitudinal 
continuity of the dental lamina is maintained nearly in the 
antero-posterior direction from 7; to zs, then almost trans- 
versely outwards for a short distance between 75 and 73, and 
then again backwards and rather inwards into the canine 
region. 
In other words, zz is situated upon the dental lamina pos- 
teriorly, in the morphological sense, to ¢z, and not morpho- 
logically on its labial side, as a coronal section by itself might 
suggest. 
In illustration of these facts, fig. 34 of a coronal section 
through 7; and 7; may be compared with figs. 35 and 36 of 
horizontal sections. These latter are taken at slightly dif- 
ferent levels, six sections intervening. In fig. 85 the swollen 
Anlagen of 7; and 7; are seen connected by the outwardly 
directed dental lamina. The peaked anterior extremity of the 
tz swelling indicates the continuation forwards of the dental 
lamina (cut obliquely) into the first incisor region. The 
rounded hinder end of the Anlage of iz is seen to end 
abruptly at this level, but this is only because the plane of 
section prevents its backward continuation from appearing. 
In fig. 86, which is closer to the oral epithelium, the lamina is 
seen to be prolonged back as a well-marked band, from the 
hinder end of the upper part of the i; swelling, through the 
canine region, to reach the first premolar Anlage (p;). 
The swollen Anlage of iz exhibits the same kind of indenta- 
tion of its fundus as that of 7;, and there is similar evidence 
