TOOTH-GENESIS IN THE CAVIID®. 287 
Summary and Conclusions. 
1. That the deciduous tooth in Cavia is the first cheek-tooth to 
develope, the tooth immediately behind it being the next to appear. 
2. That the deciduous tooth is replaced by the tooth which 
developes in front of it, which is its successor in position only, 
and is not its true morphological successor. 
3. The general pattern of the deciduous tooth resembles more 
closely that of the posterior cheek-teeth than of the anterior 
tooth. Consequently, the deciduous tooth may possibly represent 
the first of the so-called molar series. 
4. No trace of any representative of a true pre-milk dentition 
has been discovered. 
5. The presence of “concentric epithelial bodies” has been 
noted in connection with the first and third cheek-teeth. It is 
suggested that these bodies represent the last traces of milk- 
teeth. If this be correct, then it would tend to confirm the view, 
which is not accepted by all, that true molar teeth belong to the 
permanent series. It would alyo lead to the conclusion that the 
usually accepted fundamental difference between premolars and 
molars did not always hold good, the molars having milk prede- 
cessors, of which these bodies are the vestiges. 
Moreover, the presence of a similar structure in connection 
with pm.4 of Gymnura and of Canis, tends to confirm the 
opinion expressed above that the deciduous tooth is the first 
tooth of the molar series. 
6. That in the evolution of the cheek-teeth there is a tendency 
to the suppression of some cusps and a fusion of others. This 
conclusion, in conjunction with the evidences of Paleontology, 
is in favour of the multituberculate origin of the Rodentia. 
7. That the first cusp to develope is the antero-external, the 
so-called Paracone, and not the Protocone as should be the case 
according to the Tritubercular theory. 
8. That a rotation of the whole tooth takes place through an 
angle of about 45°, probably due to the peculiar conformation of 
the Rodent jaw, so that the anterior part of the adult tooth is 
represented chiefly by the external cone, the posterior part 
chiefly by the postero-internal cone. 
9. The complexity of the Rodent molars is further increased 
by involutions of the enamel, the first to appear being at the 
lingual side of the tooth, and followed by another on the external 
surface in the teeth of the Rat. 
