234 PRINCIPLES OF POULTRY BREEDING 
“The most extensive statistical work which has been carried or. 
in America is that which was done at the Maine Station from 1898 
to 1907. Here the practice was followed of breeding continuously, 
year after year, from the heaviest layers, regardless of all other 
considerations except vigor and health. The final results of this 
mass selection, after nine years’ work, did not show that mass 
selection from high producers of eggs, on the basis of the trap-nest 
records of the individuals, brought about continuous improvement 
in the average flock production, or that the progeny from the 
heaviest layers were better producers than those from birds selected 
from the general flock. These maybe considered ‘negative results.’ 
The genotype conception of heredity, on the other hand, lays 
down the fundamental truth, firmly based on breeding experience, 
that two sorts of variations can be distinguished: 
1. Those variations that are represented in the germinal matter, 
and are inherited without substantial modifications, a3 in pure lines. 
2. Those characters that are somatic * are not inherited. This 
group is not connected with germinal matter, but with the soma 
or body proper. 
It is only possible by actual breeding tests to ascertain to just 
which group a given variation belongs. 
The keynote to this latter conception of inheritance of fecun- 
dity comes from the analysis of individual pedigrees, by which 
method the behavior of each individual in inheritance can be de- 
termined. The leading thought in this new conception is, that 
the germ cell (egg or sperm) and not the body (or soma) is the fac- 
tor of primary importance in generation. For example, the indi- 
vidual’s body (somatic) characteristics are not determined by the 
body characteristics of its parents, but by the composition or con- 
stituents of the parental germ cells or gametes. Thus the size of 
a hen is not determined by the size of its parents, but by the 
gametic construction of the latter. Recent practical applications 
of this conception of the inheritance of fecundity have shown: 
1. That the gametic make-up of the male is of greater im- 
portance than that of the female; since, in the average flock, the 
*“For the student not familiar with the technical terms of biology it may 
be said that somatic is a term used to designate those characters of the organ- 
ism which pertain to all parts except the reproductive or germ cells. The 
reproductive cells are called gametes, and the adjective gametic means per- 
taining to germ cells, in opposition to somatic, which means pertaining to 
any or all parts of the organism other than the germ cells.” 
