DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES, 487 
Soon after the appearance of 72 in the sections the lamina 
completely reappears and relates itself to that tooth in a 
manner similar to that observed in the case of i+, a residual 
dental lamina, “ bud-like ” on cross-section, being present here 
also. 
The enamel-organ of 7+ is relatively shallow, having only 
attained cup-like form, while 72 is deep and _ bell-shaped, 
with pointed apex. In neither case are hard dental tissues 
present. 
We have been rather surprised to find that the enamel- 
organ of 23 in the present stage is less advanced in deve- 
lopment than that of 72. It is even a trifle less mature 
than 78, 
In the two previous stages it was the largest of the incisors, 
and, at least in Stage 11, the most advanced. Now it is found 
to lag behind as a much shallower cup-shaped enamel-organ. 
It is, however, somewhat deeply placed, and is attached near 
to the distal end of a dental lamina which is, as a whole, more 
massive here than in front. 
Another evidence of relative immaturity is found in tlie 
fact that the residual dental lamina, though distinctly indicated, 
is only as yet imperfectly liberated by differentiation from the 
enamel-organ. 
Opposite the hinder end of 7% the deep and bulky dental 
lamina abruptly diminishes in depth, and is prolonged 
backwards into the less deeply situated 74, with the lingual 
part of whose cupped enamel-organ it is directly continuous, 
much as was seen to be the case with the second lower 
molar of Stage 111. 
Behind 74 the dental lamina relates itself in like manner 
to the closely similar cupped enamel-organ of i8. Neither 
of these Anlagen as yet exhibits any traces of a residual 
dental lamina, i.e. they are as yet destitute of “ Ersatz- 
leisten.” They are decidedly less advanced in development 
than the anterior incisors. 
No trace of a milk predecessor is now found in connection 
with any of the incisors, with the doubtful exception of 
