242 MendeTs Laws of Altertiative Inheritance in Peas 
These facts show fiist that Mendel's law of dominance conspicuously fails 
for crosses between certain races, while it appears to hold for others ; and 
secoyidly that the intensity of a character in one generation of a race is no 
trustworthy measure of its dominance in hybrids. The obvious suggestion is that 
the behaviour of an individual when crossed depends largely upon the characters 
of its ancestors. When it is remembered that Peas are normally self-fertilised, 
and that more than one named variety may be selected out of the seeds of a single 
hybrid pod, it is seen to be probable that Mendel worked in every case with a very 
definite combination of ancestral characters, and had no proper basis for general- 
isation about yellow and green peas of any ancestry. 
Now in such a case of alternative inlieritance as that of human eye-colour, it 
has been shown that a number of pairs of pai-ents, one of whom has dark and the 
other blue eyes, will produce offspring of which nearly one half are dark-eyed, 
nearly one half are blue-eyed, a small but sensible percentage being children with 
mosaic eyes, the iris being a patchwork of lighter and darker portions. But the 
dark-eyed and light-eyed children are not equally distributed among all families ; 
and it would almost certainly be possible, by selecting cases of marriage between 
men and women of appropriate ancestry, to demonstrate for their families a law of 
dominance of dark over light eye-colour, or of light over dark. Such a law might 
be as valid for the families of selected ancestry as Mendel's laws are for his peas 
and for other peas of probably similar ancestral history, but it would fail when 
applied to dark and light-eyed parents in general, — that is, to parents of any 
ancestry who happen to possess eyes of given colour. 
This neglect of ancestry, the tendency to regard offspring as resembling their 
parents rather than their race, accounts for much of the apparent inconsistency 
between the results obtained by different observers who have crossed plants or 
animals. 
The writer who has most clearly recognised the importance of ancestry in 
connection with Mendel's work is Correns. In a recent summary of his views 
(No. 6) and in his fuller account of experiments in crossing races of Maize (No. 7) 
he says that between the complete equivalence of two characters and the complete 
dominance of one of them, all intermediate stages may exist, and that the 
dominance of a character varies (a) according to the individuality of different 
gametes from the same gonad ; (h) according to the individuality of the different 
plants of the same race ; (c) according to the race of the plant. He also points 
out that the offspring of pure-bred races differ in their power of transmitting 
" alternative " characters (which Correns, adopting Mendel's theory of the constitu- 
tion of gametes in this case, calls schizogonic) from the offspring of a cross, 
although the apparent characters of both may be the same. Correns illustrates 
and justifies his statements by detailed accounts of experiments with Maize ; and 
his figures of particoloured heads of seed, produced by fertilising a white-seeded 
female flower with pollen from a single male flower of blue-seeded race are most 
striking. They show that the result may be either a blue seed, or a white seed, or 
