96 On the Inheritance of Eye-colour in Man. 
Summary. 
An examination of the eye-colours of a number of parents and their 
offspring in a Leicestershire village shows that there are at least two dis- 
continuous types of iris In man :— 
(1) The duplex type, with both anterior and posterior pigments, as in 
ordinary brown eyes. 
(2) The simplex type, with posterior pigment only, the anterior pigment 
being absent, as in clear blue eyes. 
In heredity the simplex type behaves as a Mendelian recessive to the 
duplex type, which is dominant. The unit characters concerned are evidently 
presence (duplex) and absence (simplex) of anterior pigment on a basis of 
posterior pigment, presence being dominant. , 
The duplex and simplex types can be distinguished at any age. Various 
pigmental and structural changes take place in the iris during childhood and 
youth, the extent of which is not yet known. Few families with living 
parents and offspring, all adult, are to be found in one village. Consequently, 
it has not yet been possible to determine the genetic relations between the 
various shades of the duplex type. 
Note——I desire to acknowledge my indebtedness to Mr. W. Bateson for 
some valuable criticisms and suggestions in regard to the preparation of this 
paper, and also to Mr. R. C. Punnett, who came down and examined a number 
of the simplex eyes recorded above. 
(Note added 11th January, 1908.) 
Since the above paper was presented, an article on “ Heredity of Eye- 
colour in Man ” has appeared*in ‘Science,’ 1907, vel. 26, pp. 589—592 (dated 
Ist November), in which Professor C. B. Davenport independently arrives at 
similar conclusions, pointing out the Mendelian inheritance of eye-colour in 
man. 
