560 MR. M. F. WOODWARD ON [May 5, 
The discovery by Leche (9) of the extremely variable nature of 
the upper deciduous canine (Plate XXIV. fig. 9, de.) forms the key 
to his conclusions, for this enabled him to perceive that the milk 
set were in part undergoing reduction, and to formulate the belief 
that the kuob-like labial growth of the dental lamina which he found 
in connection with i.8 was the last trace of the enamel-organ of the 
milk predecessor of that tooth: from this he concluded that the 
milk predecessors to the following teeth Soe had been 
entirely suppressed. 
The conclusions may seem very bold, but their correctness is 
proved beyond a doubt by the two stages which I have been for- 
tunate enough to obtain. 
Taking as a starting-point the upper canine, I find that 
in my younger stage the enamel-organ of the permanent canine 
(pe.) is in a very backward condition, whereas labially a small 
tooth is developing (fig. 1, de.; see also Leche, Taf. iv. figs. 41 
-50); from the condition of this latter structure it is possible that 
it might develop into a small functional milk-tooth (fig. 9, 4¢-), 
and from its position and general relationship it is obviously the 
milk-canine. In the older stage we note (fig. 1a, pe-) that the 
enamel-organ of the permanent canine is more developed, and that 
attached to the labial side of the neck of this structure, i. e. the 
dental lamina, is a slight outgrowth, indenting which is a small 
irregular calcification (de.); this is in the position of the germ of 
the deciduous canine of the younger stage, and evidently repre- 
sents that tooth in a more advanced condition, i.¢. as regards 
calcification, but at the same time retrograded, for it is so small and 
irregular that it could not become a functional tooth and probably 
would not even cut the gum. Thus we see that the canine may 
vary from a functional tooth (Leche) te a minute irregular calci- 
fication of no physiological importance (cf. figs. 9 & la, de.). 
Considerable doubt has been expressed at one time or another 
concerning the exact homology of the first upper maxillary tooth 
of Erinaceus, its form in the permanent series being so unlike that 
of a typical canine, for the reason that it possesses indications 
of two fangs; moreover, it is apparently situated a considerable 
distance behind the premaxillo-maxillary suture. If, however, a 
young skull be examined (fig. 9), we find that the deciduous canine, 
when present as a conspicuous tooth, bears but a single fang and is 
situated close to the suture, as also is the developing permanent 
canine, the apparent change in position of the latter tooth being 
due to the forward extension of the maxilla, growing so as to 
embrace the premaxilla both labially and on its palatal border 
(fig. 9 a); thus the external premaxillo-maxillary suture in the adult 
is apparently situated far in front of the canine tooth. The 
true position of this tooth can be ascertained even in an adult skull 
if the palatal aspect of the latter be examined, then the canine 
is seen to be situated almost within the true suture and certainly 
not far behind it. 
