DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 507 
arrangement is a determinate and identical one. It is briefly 
as follows : 
i2 appears above the posterior portion of 74, but ona slightly 
more lateral (labial) plane. 
i2 appears directly above the posterior portion of 2. 
74 appears below the posterior end of 73, but in a slightly 
more lateral plane. 
15 appears mesially to, and on a higher plane than, 74. 
Now in Stage vir the above arrangement is departed from 
in that 74 appears not below but above 7, as well as laterally 
from it, and 7° appears directly below 7+ instead of being 
over it. 
We are unable to explain these differences (i.e. the weak 
development of 25 and the aberrant position of i4 and 7©) and 
can only set them down as instances of individual variability. 
Fig. 59 a represents the canine of the upper jaw, and may 
be compared with fig. 59, showing the same tooth in Stage v. 
These figures are especially intended to illustrate the gradual 
reduction of the dental lamina, including its “ residual’? pro- 
longation. Along with them may be taken fig. 598 from 
Stage vu, showing a still more advanced condition of 
resorption and degeneration. The figures are introduced 
apropos of Leche’s reiterated and emphatic insistence upon 
the long persistence and large size of portions of the residual 
dental lamina. We do not find these to be at all remarkable, 
though we have chosen for illustration the case of the canine, 
which provides one of the best marked and most persistent 
residual laminze amongst the anterior teeth. The three 
figures given simply show a progressive, if not very rapid, 
degeneration of the superfluous epithelial residua of the dental 
lamina. 
A residual dental lamina beside p1 and p2 is now very 
distinct. Beside dp? the Anlage of p= is labially knobbed, 
and at its fundus is present a distinct dermal papilla (cf. 
succeeding stages). Well-marked residual laminz are present 
by the lingual sides of the first two molars; and m® closely 
resembles the corresponding tooth-germ in Stage v1 (fig. 68 a). 
