TOOTH-GENESIS IN THE CAVIIDS. 269 
namely, that this tooth commences to develope earlier than the 
tooth in front of it, which I believe to replace it. 
In connection with m.2 he describes and figures both lingual 
and labial downgrowths of the dental lamina; the latter he 
interprets as a pre-milk vestige. This interpretation I shall 
discuss subsequently. The posterior molar (m.3) he states is 
not at this stage developed. 
Stage 3. Circumferential head-leneth...... 3 cm. 
body-length...... 9°3 cm. 
29 
Reconstructed diagram of Stage 5. Lettering as before. 
The incisors are now large teeth which have just cut the gum. 
No trace of any vestigial tooth is to be seen, here or in the 
diastema. 
The first cheek-tooth is well-developed though not calcified. 
The “concentric epithelial body” is clear and distinct. It 
appears to occupy a similar position relative to the edge of the 
jaw as in the previous stage; but the tooth with which it is 
connected is now more deeply placed. Its connection with the 
surface being severed, the relative position of the ‘‘ concentric 
epithelial body ” to the neck of the enamel-germ can no longer 
be definitely ascertained. The tooth itself is transversely elon- 
gated, its axis in this direction being double that of the antero- 
posterior axis. Excluding the internal and external cingula, 
representatives of two antero-posterior rows of tubercles are 
present about the centre of this tooth, as is seen in PI. 26. fig. 2. 
Of these, the outer is more pronounced, and becomes the antero- 
external cone of the adult tooth. The second cusp from the 
outer side is the second largest; it attains its maximum at a 
point in a plane slightly posterior to that of the principal cone, 
where the latter is gradually shelving upwards. In the posterior 
