1892 - 93 .] Dr William Pole on Colour-Blindness. 
131 
AP. 
Letters to Dr Pole on the Law of Heredity in Colour-Blindness. 
bth May 1880. 
Deae. Sir, — In an article of yours in the Contemporary o\\ “Daltonism” 
you remark on the immunity of women from colour-blindness. The following 
family history seems to show that this is, in a sense, compensated by a peculiar 
tendency to transmit it to their sons : — 
My maternal grandfather’s maternal grandfather {A) was a Jerseyman. I 
know not whether he was a Daltonist or not, but something odd in the family 
seems suggested by the fact that though he had seven or eight grown-up sons, 
all died childless, leaving their four sisters, my great-grandmother and great- 
great aunts, the sole representatives of the family. 
One of these ladies died unmarried ; the eldest (a) married ; the second (b) 
married my great-grandfather ; the third (c) married. 
(c) had, I believe, some sons, one of whom was colour-blind ; but that line 
of A's descendants then died out. 
(a) had, as far as I know, only one son {A.^. He was so colour-blind that he 
nearly got into trouble by writing an official letter in two colours. 
A -2 had two sons and two daughters. None of these were colour-blind. 
The elder daughter of A^ is unmarried. The younger (Ug) had a family of 
two sons and four daughters. The younger son, A^, is excessively colour- 
blind ; the rest of the family are free. 
My great-grandmother (b) had three sons and two or three daughters, who 
married. The posterity of her daughters is numerous, and I have never heard 
of colour-blindness among them, or that they were colour-blind themselves. 
The eldest brother of my grandfather was faintly colour-blind. He had 
many sons and daughters, first cousins of my mother, none of whom were 
colour-blind. I think none of the daughters have left children. 
The eldest married son of my great-uncle has four sons, eight daughters, and 
a daughter’s son, all free. The only other married son of my great-uncle left four 
daughters, who have most of them large families, but none of them are colour- 
blind. My grandfather’s younger brother was free from colour-blindness, and 
so was his family, but it was small and has died out. 
My grandfather, B, who was very colour-blind, had about sixteen children, 
none of whom were colour-blind. His sons, my uncles, have large families 
of sons and daughters, and several of them have grandchildren ; but colour- 
blindness is unknown among them. 
On the other hand, his five married daughters, my mother and four aunts, 
have the following families : — 
First Aunt (b. 2 ). — Two sons, a daughter, four or five sons’ sons, and a 
son’s daughter. Bg, the elder son, my first cousin, is colour-blind ; 
his brother, sister, sons, daughter, and nephews are free. 
Second Aunt (bg). — Three sons and several daughters, and the children 
of a son and of some daughters. My aunt’s eldest son, Bg, is 
colour-blind, the rest of her posterity free. 
Third Aunt (b 4 ). — One son, B 4 , excessively colour-blind. 
My Mother (bg). — Seven sons, three daughters, and a son’s son and a 
son’s daughter. My eldest brother, B^, my third brother, B^, and 
I, the sixth son, B^, are colour-blind, the rest of my mother’s pos- 
terity free. Though I was the youngest patient, my colour-blind- 
