126 PROF. DR. L. BOLK 



and exhibiting itself by the occasional development of two or 

 perhaps three rudimentary teeth which alternate with the nor- 

 mal molars, the principal result of this examination. Therefore 

 the subjects of the two sections show a common feature, con- 

 cerned with some question about the phylogenetical development 

 of the molar region of man. This common characteristic makes 

 the combination of the results of both investigations possible. In 

 doing this we get a more complete insight into the natural struc- 

 ture of our dentition. In the most compendious manner, such 

 a combination is given by a scheme in which the elements of 

 both dentitions are represented in their topographical relation 

 to each other. The knowledge of such a scheme is desirable, as 

 a starting point for further investigations, after the subsequent 

 changes in our dentition. For, as we hope to demonstrate in the 

 next paragraph, changes identical with those which have taken 

 place in the past, will occur again in the future. 



I shall begin by recording once more the dental formula of the 

 Platyrrhinae and Catarrhinae, in their natural relations: 

 Dental formula of Cebidae: 



ii. io. c. nil. nio. nis. 

 Ii. L. C. Pi. Po. P3. Ml. Mo. ^13. 



Dental formula of Hapalidae: 



ii. i2. c. mi. nio. nia. 

 Ii. L. C. Pi. l\. P3. Ml. M,. [M.3] 



Dental formula of Homo: 



ii. io. c. nil. nio. Mi. 



ii. I,, c. Pi. p,. [P3] M2. yu. [Di] 



The teeth reduced and lost, during the progress of himian evo- 

 lution, are placed in brackets. The so-called fourth molar in 

 man, which, as demonstrated in the first section, is homologous 

 with the third molar of the platyrrhine monkeys, is indicated 

 as Distomolar (Di). In the three formulas, expression is given 

 to the natural topographical relationship of the elements of 

 the two dentitions to each other, by the alternation of the 



