488 J. T. WILSON AND J. P. HILL. 
the first. We have seen above that the vestiges of such 
present in Stage 111 were already retrogressive, that of di3 
being in process of invasion and dispersion by connective- 
tissue ingrowth. 
The canine calls for little remark. It is a large and deeply 
cupped enamel-organ (fig. 47), and its future residual dental 
lamina is only very partially indicated as a somewhat bulky 
projection from the side of the enamel-organ. The drawing, 
however, contains a highly interesting feature in the shape 
of an attenuated cord of cells (d‘) with a slightly clubbed 
termination, springing from the labial side of the dental 
lamina near where it is continuous with the oral epithelium. 
This appears in only a very few sections, abruptly disappear- 
ing fore and aft, and is without doubt the retrogressive 
vestigial representative of the perfect miniature cupped 
enamel-organ of the milk canine figured in Stage m1 (fig. 
20 d?). Since this is all that is left of such a perfect rudiment 
as that in Stage 111, itis not surprising that the much more 
rudimentary milk incisor structures seen in Stage 111 should 
have wholly disappeared. 
Behind the canine the dental lamina, losing much of its 
depth, but still remaining pear-shaped on cross-section, is 
continued bodily into the first premolar Anlage. . 
Both the first and second premolars are now deeply cupped 
enamel-organs of au equally advanced stage of development to 
that of the canine (fig. 47), which they now much resemble. 
In the case of each a residual dental lamina is just being differ- 
entiated. In this respect, but not otherwise, p+ is just a little 
in advance of p2. 
At its hinder end p2 tapers away into the undifferentiated 
dental lamina, which here remains tolerably thick and club- 
shaped on cross-section. On its being traced backwards, there 
soon appears by the side of the dental lamina, but at a consi- 
derable distance from it, the enamel-organ of the deciduous 
premolar. This is not only placed labially, but is situated low 
down, i.e. close to the oral epithelium. It has now attained 
some degree of complexity. One can easily distinguish a 
