DEVELOPMENT AND SUCCESSION OF 1 EETH IN PERAMELES. 471 
So far as we can ascertain, there is not to be discovered 
either in the present or in the preceding stages any such dif- 
ferentiation in the first incisor region as might be taken to 
represent there the rudiment of a true milk-tooth, i.e. one 
which belongs to a tooth generation preceding that to which 
the first permanent incisor belongs. Nevertheless there is 
some reason for the belief that traces of an attempt at the pro- 
duction of such a tooth do appear at some time during the 
development of the teeth in Perameles. And if any such 
rudiment does occur, then the cell material of which it consists 
must be derived by outgrowth from the labial side of the base 
of the mass we have described as constituting the Anlage of 
the first incisor. It has been stated above that in its size and 
degree of differentiation (including that of a “milk” rudi- 
ment) the third incisor Anlage is the most developed member 
of the upper incisor series at the present stage. The second 
is less developed, but yet exhibits features similar to those in 
the third. So also in the case of the fourth and fifth incisor 
Anlagen. Although, therefore, no such labial remains occur 
in connection with the first incisor Anlage in Stage 1ir as we 
have been able to show associated with the incisors behind it, 
and more especially in the canine region, we consider ourselves 
justified in the belief that certain cellular processes situated 
on the labial side of the root of the dental lamina in the first 
incisor region of the next stages (1v and v) may possibly 
represent the remains of the missing rudiment of a dit. In 
the present stage we may suppose that the latter is not struc- 
turally defined from the basal portion of the common first in- 
cisor Anlage. 
In further corroboration of our views upon the incisor 
development in Perameles it may not be inappropriate to 
refer to the condition we have found in another polyprotodont 
Marsupial, Dasyurus viverrinus. Among our series of 
stages of development of this form we possess one which, in 
respect of the third incisor, exhibits a general stage of de- 
velopment intermediate between the present stage (111) and 
the following stage (1v) of Perameles. 
