148 PROF. DR. L. BOLK 



judged as a reversion or atavistic variation. The morphologist 

 of that time will consider such a variation as testifying to that 

 past state of primate denture, when two premolars were normally 

 present, in just the same manner, as in the case of figure 5 we 

 may judge the additional tooth to be a reversion to the past 

 state in which three premolars participated in the composition 

 of the denture. 



As a final remark I will call attention to the fact that a com- 

 parison of the conditions represented in figures 5 and 28, fur- 

 nishes a strong argument in further support of my view that the 

 first permanent molar of the catarrhine Primates, was originally 

 the hindmost or third milk molar. 



The sections of this communication treat principally of three 

 problems, concerning respectively the past, the present and the 

 future state of human dentition. And although the subjects of 

 these sections are quite different, there is something common in 

 the manner in which the problems are treated, and the stand- 

 point from which they are viewed. This common standpoint i;^' 

 based on the preponderant value accorded, in the three sections, 

 to the variations in our dentition. This point especially calls for 

 remark, since some authors are determined to diminish the sig- 

 nificance of dental anomalies, with regard to the study of the 

 developmental history of our dentition. In the course of this 

 article there has been occasion to point out that I cannot concur 

 with this opinion. I believe, on the contrary, that just these 

 dental anomalies furnish the most valuable data from which to 

 build up the developmental history of this part of our organism. 

 But it is necessary that we learn to interpret these data. In this 

 paper I ha\'e shown how I have interpreted some of these. I 

 hope my interpretations have been correct. 



