576 MR. M. F. WOODWARD ON [May 5, 
On making an examination of the clarified jaws (Plate XXVI. 
fig. 29) of ayoung animal (hairless), one is immediately struck with 
the correctness of the greater part of these figures, but in respect to 
the first premolar they appear to be incorrect, for no trace is observ- 
able of Bate’s dpm. 1. In order to be certain that I was not dealing 
with an abnormal specimen, I examined the clarified Jaws of three 
specimens of about the same age as that studied by Bate, two others 
being cut one into horizontal and the remaining into frontal 
sections; three younger animals were also examined by the section 
method!. In all 10 half heads were investigated, and as these, 
obtained from various localities, all agreed amongst themselves in 
respect to the relations of the 1st premolar, I cannot but come to 
the conclusion that Bate’s observations on this point are erroneous, 
and that the teeth which he describes as = nel 
pm. 1 
In the younger specimen all the deciduous teeth save the 1st 
premolar were well calcified, but the germs of the permanent teeth 
though distinct were but little differentiated. An examination 
of a horizontal section at this period (figs. 27 and 28) shows pm. 1 
developing in a position precisely similar to that occupied by the 
reduced deciduous incisor, canines, and premolars; and, as is the 
case with the latter, the former exhibits a specialized portion of 
the dental lamina on its lingual surface, the only observable differ- 
ence being that dpm. 1 is larger, uncalcified, and generally more 
backward than the other milk-teeth ; also that the germ of ppm. 1 
is slighter but might well be thought capable of developing at 
a Jater period. That this is not the case is seen from an examina- 
tion of the older stage: here all the deciduous teeth are strongly 
developed and even dpm. 1 is now calcified (fig. 31); it is, 
however, very large and not at all of the nature of a vestigial 
needle-shaped tooth such as figured by Bate, but rather presents all 
the characteristics of the tooth regarded by him as ppm. 1. The 
permanent incisor, canines, and premolars (fig. 30) are now highly 
differentiated, with Jarge enamel and dentine germs : a comparison 
of one of these with the indication of the germ of ppm. 1 
(Plate XX VI. fig. 31,d./.), shows that the latter is now Jess marked 
than in the earlier stage and is obviously aborting ; consequently we 
may safely assert that it never attains any degree of specialization, 
but remains merely a slight swelling of the dental lamina. 
The entire absence of any labial development from that portion 
of the dental lamina between the large enamel-organ of this tooth 
(dpm. 1) and the epithelium of the mouth, taken together with the 
position occupied by it, viz. one similar to that of the true milk- 
teeth, and the specialized thickening of the dental Jamina on its 
lingual side, exactly resembling in appearance and position the true 
have no existence. 
1 Jn all 3 stages were examined, including two specimens of stage 1, one of 
the 2nd, and five of the 8rd stage, all being older than Leche’s stages. 
(1) 55 mm. total length ; 17 mm. head length. 
8 
(2) 58 ” ” ” 1 ” ” ” 
(3) 95 ” ” ” 30 ” ” ” 
