DEVELOPMENT AND SUCOESSION OF TEETH IN PERAMELES. 489 
protocone, deep and pointed, from the shallower and less 
pointed paracone and metacone, in front and behind. 
The inner epithelium is elongated and cylindrical, especially 
at the apex of the protocone, where the cells are about as long 
again as elsewhere, and their inner halves are pale and un- 
stained, the nuclei forming an outer marginal band. Covering 
the tip of the papilla of the protocone there is an exceedingly 
thin dentine cap, the only one hitherto encountered in the 
upper jaw (fig. 48). Outside the inner enamel epithelium the 
stratum intermedium forms a very distinct layer of cubical 
or flattened cells, and outside this again the stellate enamel 
tissue is reduced to a comparatively narrow layer. 
As it is traced backwards into the region of dp®, the dental 
lamina increases in thickness, and opposite the paracone it 
begins to exhibit remarkable modifications of its swollen free 
marginal portion in the shape of alternate constriction and 
enlargement, the constrictions being due to ingrowth of con- 
nective tissue on the labial aspect of the lamina. The thickest 
portion of the lamina is opposite the protocone (fig. 48, 7di.), 
where also the connection between dp* and the swollen dental 
lamina becomes apparent. 
Fig. 49 represents a horizontal section through the region 
between p2 and m+; the level is too high to show the very 
lowly situated dp® at all well, it is indeed only shaved through 
near its higher or basal limit. 
The tapering of p2 into the dental lamina, and the prolon- 
gation of the latter by the sides of dp? and m4, is strikingly 
shown; also the peculiar modification of the lamina which has 
been referred to as taking place opposite dp. 
It can hardly be gainsaid that here we have the earliest 
promise of the specific differentiation of p®. But we are not 
at all clear as to the significance to be attached to the con- 
stricting ingrowths of connective tissue described and figured. 
They are also present in similar shape in Stage v (fig. 50). 
At first sight they suggest papilla, but not only are they histo- 
logically entirely unlike the Anlagen of papille (for instead of 
being cellular growths they are fibrous bands), but an exami- 
