188 HALFDAN BRYN 



— 1 year old 1,23 



1 — 2 years » l,4i 



2 — 3 » » '. 1,59 



3 4 » » 1,87 



4 — 5 years old 2,o3 



5 — 6 » » 2,11 



6 — 7 » » 2,27 



7—50 » » 2,26 



From the age of eight there is no traceable change. The im- 

 portant change in this connection, e. g. the change from plain blue 

 eyes to traceable pigmentation takes place much earlier in most 

 people, probably within the age of two. Concerning the eye colour 

 it is reasonably safe to assume that no mistakes are done in grouping 

 the children in »simple» and »double» eyed when two or three years 

 old. The change which takes place later and which makes the index 

 grow till the age of eight only consists in an intensification of the faint 

 pigmentation. 



If the material is examined as to the parents' group and the 

 cildren's group particularly in the tendency here mentioned, the fol- 

 lowing scale is found: parent's groups 43,5 per cent double, and 56,.) 

 per cent simple, children's groups 43,o per cent double and 57,o per 

 cent simple. Even these figures make plain the extraordinary con- 

 stancy of these characters. — Before discussing at length the results 

 of my own investigations I shall shortly state the results of some of 

 the best known investigations already made in this subject. One of 

 the best known studies is published by Gertrude Davenport and 

 Charles Davenport^. This work includes the examination of 85 child- 

 ren from 28 families. The examinations were done by teachers and 

 friends. They classified the eyes in 8 types. The classification was 

 too minute in the opinion of the writers. It is said that 3 classes would 

 have been sufficient: blue eyes, bluish-green or bluish-brown ones and 

 brown eyes. The authors draw very far-reaching conclusions from 

 these investigations: 



1. A blue eye colour is recessive to a brown one. Two parents with 

 blue eyes will therefore only have children with blue eyes. — If 

 you examine their material carefully, this conclusion seems, 

 however, premature. To arrive at the above conclusion is to dis- 

 regard the results of their own investigation: »Of the offspring 

 of two blue parents 69 are blue and 6 blue-gray or gray. Two 

 additional cases of so called »hazel» eyes, we suspect to be of a blue 



^ Gertrude Davenport and Charles Davenport: Heredity of Eye colour in Man. 

 Science, XXVI, 1907. 



