ae 
SECTIONAL TRANSACTIONS.—M. 461 
The first of each pair is dominant, and the second recessive. In the course 
of the experiments more than 50,000 eggs were recorded, and each egg was 
weighed and graded for size and colour. In order to analyse the complex 
and continuous data of egg-production a system of uniform gradings was 
formulated which ultimately led to the identification of the factorial pairs. 
The somatic gradings are based throughout on the genetic factors concerned, 
so that each hen has its somatic and genetic characteristics combined in a 
single formula. Production is graded in percentages. 
SUMMARY OF THE RESULTS IN WHITE LEGHORNS AND WuHitE WYANDOTTES. 
Ob- 
served 
Characters Totals Dominant Expected Recessive Mela a Expected 
Sexual ma- 
turity .| 335 | Early(E) . | 286 | 289:00 | Late (e) .| 49 46:00 
Winter rate | 266 | Fast(W) . | 231 | 231°75 | Slow(w) .| 35 34°25 
Spring rate | 224 | Fast(S) . | 216 | 217-25 | Slow(s) . 8 6°75 
Autumn rate| 194 | Slow(M) ./| 140 | 145°50 | Fast(m) .| 54 48°50 
Broodiness . | 201 | Broody (H) 50 58°50 | Non-B. (h) | 151 | 142°50 
Egg-size . | 331 | Small(N) . | 135 | 128-75 | Large (n) . | 196 | 202-25 
Egg-colour. | 331 | Brown (C) . | 137 | 142:00 | White (c) . | 194 | 189-00 
Totals. 4/1882 — 1195 | 1212°75 — 687 | 669-25 
Eighteen definite exceptions appeared, of which two proved to be somatic 
and not genetic, eleven were slight exceptions probably of the same nature, 
three were pathological, one was possibly an incomplete dominant, while one 
was apparently a true mutation. 
Pearl’s discovery of two genetic factors for winter-production in Plymouth 
Rocks (1912), confirmed by Goodale in Rhode Island Reds (1918-19), is also 
confirmed in White Leghorns and White Wyandottes, in which the presence of 
both E and W factors is necessary for high winter-production. 
No sex-linkage was found in either of the production factors of the Leghorns 
or Wyandottes used, and in this respect these two breeds resemble Goodale’s 
Rhode Island Reds rather than Pearl’s Plymouth Rocks. 
There is a definite difference of rhythm between the discontinuous Slow (w) 
and the discontinuous Slow (s) birds, and it is possible that the Slow (s) birds 
are pathological. 
Slow (M) birds are deep autumn moulters, while Fast (m) birds are partial 
autumn moulters. 
A sensible proportion of broody hens do not show broodiness until their 
second season, so that it was not possible to ascertain in all cases the true 
nature of the ‘ Non-Broodies.’ 
The appearance of a few broody exceptions in the Leghorns gives support 
to Punnett’s (1920) suggestion of the possible presence of an inhibitor to the 
broody factor in certain non-broody birds, and an HI scheme of broodiness 
does bring into line many of the complicated and conflicting data published. 
To demonstrate this satisfactorily, experiments on a considerable scale would 
be required. 
The results indicate the gradual evolution of the increase of fecundity in 
the hen by a succession of definite and discontinuous steps or mutations. Early 
maturity, fast winter rate, fast spring rate, and possibly brown-egg are dominant 
mutations, while fast autumn rate, large-egg, and possibly non-broodiness are 
recessive mutations. A single case of the occurrence of a recessive mutation 
for large-egg was observed, which originated in a Wyandotte cock. The experi- 
mental matings made were not suitable for testing satisfactorily the question 
of linkages of the above factors. 
Economic Significance of Results —Pure and permanent strains of high 
producers of large eggs can be made by the elimination of birds carrying 
ewsMHN factors in accordance with the factorial scheme presented. 
EWSmbhn birds are the best layers, and EEWWSSmmhhnn birds 
