212 HALFDAN BRYN 



The dolichocephalic part of the parents is in this case only phe- 

 notypically dolichocephalic. They are actually^- variants of the com- 

 mon northern type with index 77 à 78. 



I think this last explanation the most probable. The dolicho- 

 cephaly is never so marked as in Tydalen. 



If this explanation is correct the tables 12 and 13 will be found 

 fairly well in accord with the Mendelian laws, the brachycephalic pa- 

 rent being a heterozygote and the other a homozygote mesocephal: 

 BM X MM = 2 BM + 2 MM. 



Nothing corresponding to what I have stated in table 8 is to be 

 found in Jorgensen's large collection from the Faroes. 



However, in his material there are found many cases of segrega- 

 tion. A smaller or larger part of the offspring has often higher or 

 lower indices than any of the parents corresponding to my results in 

 tables 5 and 6. 



The non-conformity found between Jorgensen's material and the 

 present material is entirely due to the fact that the strongly dolicho- 

 cephalic type of Tydalen described by me is not to be found in 

 the Faroes. 



In the chapter, where Jörgensen deals with index cephalicus in 

 families, he states, that he has 11 families, where both parents are 

 dolichocephals. He uses, however, Broca's classification. Not one 

 case of dolichocephaly in both parents would have been found in his 

 large collection if the classification used by me (mesocepi.als 76 — 80) 

 had been employed, whereas 2 cases are found in my small collection 

 from Tydalen. 



It is, therefore, justified to say, that Jorgensen's material is in 

 no respect in disaccord with the material from Selbu and Tydalen 

 produced by me. The conclusions to be drawn from the present study 

 seem to be the following: 



1. Three biotypes are found in Selbu and Tydalen with regard to 

 index cephalicus, whose indices are about 73, 77 and 83 re- 

 spectively. 



2. These types segregate when interbred in accord with the Mende- 

 lian laws in everything essential. 



3. The brachycephalic type is dominant to both the others. 



4. The dolichocephalic type is too rare to allow any positive conclu- 

 sions; it seems, however, to be dominant to the mesocephalic type 

 and .recessive to the brachycephalic type. 



