476 J. tT; WILSON AND JS. P.-Hiih. 
dental lamina, opposite the anterior half of p2, there is to be 
seen through several sections a small mass of cells projecting. 
It is possible that this is representative of dp2. If so, it is 
very degenerate, and there is no similar structure beside the 
Anlage of p+, though a similar small cell-mass is present in 
the lower p2 (see below). 
The epithelial projection in question is at all events not due 
to a bending of the lamina, whose “neck” is short, straight, 
and perfectly preserved in the region referred to. 
It will be remembered that in the preceding Stage 11 no 
trace of localised thickening or other differentiation was ob- 
servable in the premolar region of the dental lamina in front 
of the site of the third premolar, but that here a tooth Anlage 
in the cup-shaped stage was already present. And whilst in 
the present stage the rudiments of the two anterior premolars 
(p+ and p2) are sufficiently defined as such by localised en- 
largement of the dental lamina, the Anlage of that premolar 
tooth which was already cup-shaped in the preceding stage is 
now still further advanced, showing differentiation of the 
stellate reticular tissue of the enamel-organ (figs. 22 and 24). 
Furthermore it is to be remarked that the process of libera- 
tion of dp® from the lingually-placed dental lamina, which was 
stated to have just set in the preceding stage, has progressed 
considerably, so that the freed dental lamina (fig. 24, rdJ.) 
now forms a partly independent epithelial ingrowth by the 
lingual side of the tooth rudiment. The latter is still seen 
(fig. 24) to be somewhat broadly attached to the labial aspect 
of the liberated lamina at some distance from its apex, or, 
strictly speaking, from its free distal margin, and extending 
nearly to its attached proximal margin or “ neck.” 
A careful investigation of the earliest stages of 
premolar tooth-differentiation has thus served to 
show that this third in order among the premolars is 
not differentiated at all contemporaneously with the 
1 The question of the significance of certain outgrowths of the dental 
lamina on its labial side is discussed below in connection with the molar 
problem. 
