4.64 J. LT. WILSON AND <3. OP. ATE 
organ is at length evolved by this process, the outer part 
of the rim of the cup is constituted by the labially 
outgrowing lobe, and the inner part of the rim of the 
cup is formed by the main body of the dental lamina 
itself. It will be observed that this explanation is essen- 
tially in agreement with the idea expressed in Rése’s simile 
regarding the relation of the cupped enamel-organs to the 
dental lamina, when he says they are arranged “like swallow- 
nests on a board.” Our present stage illustrates the condition 
found just prior to the actual ‘“swallow-nest” stage of 
differentiation of the enamel-organs. At this stage, indeed, 
“sulcus” is the term which more adequately expresses the 
character of the depression corresponding to the future cup of 
the enamel-organ. It is open both fore and aft, because it 
owes its first formation to a mere labial outgrowth of some- 
what inchoate character. It may be noted further that this 
sulcus may be very shallow, or even absent, if the outgrowth 
of cells takes place near to the free margin of the lamina and 
extends simply outwards. Thus in the figure given (fig. 11) 
of the first upper molar Anlage in Stage 11 the labial promi- 
nence is so wide, and extends so near to the free margin of the 
lamina, that the intervening sulcus is broad and extremely 
shallow. The cellular condensation indicative of the future 
dermal papilla is, however, unmistakable. So also, with some 
difference, in the Anlage of m4, Stage 11 (fig. 15). 
The definitive cupping of such a bilobed enamel-organ of 
course involves the subsequent appearance of a margin or rim 
to the cup both in front and behind, in consequence of the 
more pronounced local limitation of the processes of enamel- 
organ formation,—processes which at first operate along a 
stretch of dental lamina indefinitely limited fore and aft. 
As may be gathered from Rése’s ‘ swallow-nest ” compa- 
rison, the lingual wall of the cupped enamel-organ is formed at 
first simply by the dental lamina,—the “ board ” against which 
the “‘swallow-nests ” are placed. But by-and-by, as we shall see 
hereafter, this dental lamina undergoes further differentiation, 
whereby a proper and distinct inner wall is contributed to 
