MENDELIAN CHARACTERS IN PLANTS AND ANIMALS. 125 
(a) Coat colour, five pairs, viz. coloured and white (see figs. 27 and 28), 
grey and black, grey and yellow, black and yellow, full and dilute (full 
colours are grey, black, and yellow, and their respective dilutions blue- 
grey, blue, and fawn). 
(6) Coat patterns, eight pairs, viz. Himalayan white and clear white, 
tortoise-yellow and clear yellow, self-coloured and Himalayan white, 
English-marked and self-coloured, tan-marked and self-coloured, Dutch- 
marked and self-coloured (the heterozygote of this is variably marked), 
English-marked and Dutch-marked, plain and silvered. 
(c) Coat length and texture, one pair, viz. short and angora (see figs. 
27 and 28). 
With regard to the five Mendelian pairs of coat-colours, the first four 
might be regarded, as Mr. Bateson suggests, as presence and absence of a 
specific colour, presence being dominant. The original grey might be 
regarded as based on black and yellow, black being absence of grey, and 
yellow being absence of black and grey. The remaining pair, full and 
dilute, may be regarded as presence and absence of full on a dilute basis, 
presence being dominant. 
With regard to the eight Mendelian pairs of coat patterns, all may be 
regarded as presence and absence of colour in certain areas, presence 
being dominant, except in the English and tan patterns, where presence 
is apparently recessive. 
With regard to the one pair of Mendelian characters for coat length 
and texture, short and angora, the application of the presence and absence 
hypothesis is not so obvious. If we regard this as presence and absence 
of short on an angora basis, we have the difficulty that the long coat of 
the angora appears to be a lengthened short coat. If, on the other hand, 
we regard it as presence and absence of angora on a short basis, this would 
imply dominance of angora over short in the zygote, while experiments 
show, on the contrary, that short coat is dominant over angora coat. 
PoutTry. 
In my experiments with poultry, eight pairs of Mendelian characters 
were met with, viz. rose and single comb, leaf and single comb, extra toe 
and normal foot, crested and plain head, feathered and clear shanks, white 
and yellow shanks, white and black plumage, white and buff plumage ; 
the first-named of the pair being dominant over the other, which is 
recessive. 
With regard to the combs, we have already seen that the unit-characters 
may be regarded as presence and absence of rose, presence and absence of 
leaf, presence being dominant, absence of either being single comb on 
which the rose and pea are presumably based. (It is possible also that the 
large single comb of the Mediterranean races is a separate unit-character 
based on the original small single comb.) 
With regard to the foot characters, the dominance of extra toe over 
normal foot was found to be both incomplete and irregular, but segrega- 
tion and gametic purity were evident, the unit-characters being apparently 
presence and absence of extra toe, presence being usually dominant. 
With regard to shank feathering, dominance of feathered over clear 
