DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 479 
Lower Jawof Stage III.—The phase of tooth develop- 
ment exemplified in the lower jaw is on the whole a little in 
advance of that found in the upper. This is more notable in 
some regions than in others. During the period of development 
which intervenes between Stages 11 and 111, rapid advancement 
has been made in the differentiation of the first lower incisor 
Anlage. An attentive comparison of our figures of sections 
through this region in the two stages (figs. 12 and 388) will 
chiefly show that the early papillated Anlage of di, in Stage 1 
has rapidly passed through the succeeding stages of its 
development up to and including the development of a perfect, 
though thin, dentine cap for the papilla. No enamel has been 
formed, but the enamel-organ—apparently arrested in its 
evolution—has become separated from the main mass of the 
dental lamina by a considerable interval, remaining connected 
with it only by a delicate and disintegrating strand of 
epithelial cells forming a “ Verbindungsbriicke” (fig. 
33, cb.). 
It may be noted that the position of diz relative to the 
Anlage of 7+ appears to have altered during the transition from 
Stage 11 to Stage 111. In the former the rudiment of di> 
occupied the labial aspect of the more anterior portion of the 
swelling corresponding to 77. Here, however, the differentia- 
tion and segregation of diz have allowed of a growth forward 
of the bulky Anlage of i;, unhindered by the presence of any 
more anterior dental element. Hence, in the present stage, 
the vestigial dit has come to lie opposite the more posterior 
moiety of its large morphological successor. The relative 
forward extension of the latter appears to continue at least up 
to a period represented by our Stage 1v (see fig. 56). 
We have in the next place to point out that, in the present 
stage (111) the dental lamina, which was almost wholly 
undifferentiated from the enamel-organ of diz in Stage 11, has 
gone on to form the large papillated dental germ of 7; (fig. 33). 
But as yet there is no trace of differentiation of a residual 
dental lamina from the Anlage of 71. In the succeeding Stage 
tv, however, a residual lamina, with its free marginal portion 
