148 
The palatine teeth of the alternating series are 6—7 in number, 
and are all fully formed in an individual 18 cm in length. After this 
period there is a temporary cessation of tooth formation, and on its 
recommencement the teeth are, as in the other cases, uniform in size 
(Fig. 4b). At a stage when the anterior members of the uniform 
series are only just beginning to develop in the palatines, there are 
already several fully formed in the lower jaw, but no trace of them 
in the maxilla. 
The vomerine teeth, when present, appear to commence their 
development towards the end of the incubation period. They afford 
no satisfactory data bearing on the question to be discussed. 
St E.d. St 
> den. 
EN 
TEILT, 
er 
i 
FR 
Fig. 5. Sagittal seetion of mandibular alternating teeth (seventh and eighth, right 
side), illustrating fusion which occurs between the teeth of two dentitions. den. dentary, 
E. d. tooth of embryonic dentition, within the epidermis, St. remains of stellate tissue 
of enamel organs, sp. shrinkage cavity. (Embryo in last month of incubation. Length 
of skull 11,5 mm. x 100.) 
opposing teeth. It is possible that in some cases the lower teeth have 
three components, though my specimens do not support this view. In 
most of the existing figures the amount of tooth substance is exaggerated, 
especially in the case of the premaxillary. This is partly owing to the 
mistaken idea that each premaxilla had one large tooth, notched at the 
apex. A more recent view, that the form of the front teeth is due to 
fusion, is equally erroneous. There is no fusion, and the appearances 
are entirely due to the close relations of the simple, sub-conical teeth, 
to the bone, which grows out some distance beyond the gums and is 
subject to the grinding action of the opposing jaw, after the enamel 
and dentine are worn away. 
