94 Mr. C. C. Hurst. [May 7, 
breeds true to the simplex character without reversion to its duplex 
ancestors. In view of recent Mendelian experiments with plants and animals, 
it did not seem impossible that some simplex individuals at least might 
be carrying factors which on meeting, in the process of fertilisation, with 
other complementary factors, might give rise to reversions of the duplex 
type, but, so far, no such cases have been found. For the present, therefore, 
while remembering such a possibility, we must take it that the duplex and 
simplex types of eye-colour in man constitute a simple Mendelian case 
of presence and absence of a certain pigment. 
With regard to the different patterns of duplex eyes and their various 
shades, my facts, so far, do not enable me to determine positively their 
genetic relations. The chief difficulty is due to the fact that the anterior 
pigment present in children tends to increase with age, though to what 
extent, or to what age,is not yet known, owing to the limited period of 
observation. 
In the few families observed, with all adult offspring, the evidence suggests 
that the ringed pattern is recessive to the self-coloured pattern, which is 
dominant ; but with regard to the genetic relations of the spotted pattern to 
the ringed and self-coloured patterns there is practically no evidence 
available. 
Previous Work. 
Large numbers of records of eye-colours have been compiled and discussed 
by anthropologists and biometricians at home and abroad. In most cases, 
however, the data relate to certain sections of the population, such as school 
children and conscripts, not analysed or grouped according to their families. 
So far, I have found only two memoirs which approach the question of the 
inheritance of eye-colour in man by a comparison of parents with their 
offspring. The first is that of Alphonse de Candolle.* 
De Candolle, with the assistance of some 28 experienced observers, 
collected a number of records of the inheritance of eye-colours in Switzer- 
land, Germany, and Sweden. De Candolle made two classes of eye-colours, 
“brown” and “ blue,’ omitting all doubtful shades. The “brown” class 
included “black,” “brown,” “ yellow-brown,” and “green-brown.” The 
“blue” class included “blue,” “blue-grey,” “grey,” “green-blue,” and 
“green-grey.” Comparing de Candolle’s classes and shades with mine, it is 
evident that all the “ brown” class belong to the duplex type with anterior 
pigment, but that only part of the “blue ” class belong to the simplex type, 
without anterior pigment. 
* “ Wrérédité de la Couleur des Yeux dans |’Espéce Humaine,” ‘ Archives des Sciences, 
Geneve (3¢me période, vol. 12, 1884, pp. 97—119). 
