MERISTIC VARIATION 



49 



3. Skull (orang) No. 2043 a, Oxford Museum, is normal except as to the 

 second premolar in the upper jaw (j& 2 ). Both these teeth are missing from 

 their proper place. There is plenty of space on the left side but somewhat 

 less than the normal on the right side. The missing tooth of the right side 

 is present in the skull, but instead of being in its proper place it stands up 

 from the roof of the mouth within the arcade immediately in front of the 

 right canine and almost exactly on the level of the second incisor, being in 

 the premaxilla at some distance in front of the maxillary suture. 



Discussing this case, Bateson observes : 



That this tooth is actually the second premolar which has by some means 

 been shifted into this position there can be no doubt whatever. It has the 

 exact form of the second premolar and is of full size. It stands nearly verti- 

 cally, but is a little inclined towards the outside. The canine is, by the 

 growth of this tooth, slightly separated from the second incisor, and the first 

 premolar is consequently pushed also somewhat further back. Hence it 

 happens that the diastema space for the second premolar on the right side 

 is not of full size. This should be understood, as it might otherwise be 

 imagined that the contraction was due to a complementary increase in the 

 size of the other teeth, of which there is no evidence. 



The missing premolar on the left side was not visible, but " on 

 the left side of the palate there was a very slight elevation at a 

 point homologous and symmetrical with that at which the second 

 premolar on the right side was placed. ... A small piece of 

 bone was here cut away, with the result that a tooth of about the 

 same size and formation as / 2 was found imbedded in the bone." 

 In this case, therefore, the upper premolars on both sides had 

 " traveled away from their proper positions and taken up new 

 and symmetrical positions in the palate, anterior to the canines." 



As Bateson pertinently remarks (italics and parenthesis mine), 

 " The facts of this case go to show that the germ of a tooth con- 

 tains within itself all the elements necessary to its development in 

 its ozvn true form [even in an abnormal position], provided of 

 course that nutrition is unrestricted." This is a significant point 

 of peculiar interest to students of thremmatology, not because of 

 its bearing upon dentition but because of the light it affords upon 

 the basis of variability and the ultimate units of variation. 



4. Gorilla from the Congo, with a fifth incisor standing almost in the 

 middle of the lower jaw. It has the characteristic chisel shape of the incisor, 

 but it is turned half round so that the plane of its chisel stands obliquely." 



