38 THE TREND OF THE RACE 
shoulders of the Mendelian to those of his opponent. But if it is 
granted that a characteristic is transmitted according to Mendel’s 
law it remains to be determined whether it presents a simple 
typical illustration of such transmission or follows a more complex 
type of Mendelian inheritance. Where several factors are in- 
volved, inheritance, though Mendelian, may present the appear- 
ance of the old-fashioned blending type, and should be dealt with 
in practice as though it were truly blending. 
Let us suppose for instance that feeble-mindedness depends 
not upon the loss of a single factor in the germ plasm, as com- 
monly assumed, but upon the presence of many such factors 
belonging to different allelomorphic pairs. The matings of two 
feeble-minded persons, thus bringing together two germ plasms 
generally tainted with defectiveness, would be expected to produce 
nothing but feeble-minded offspring. The matings of a normal 
with a feeble-minded person migh tbe expected to produce variable 
results. Various factors affecting mentality in the normal individ- 
ual would doubtless tend to give rise to various degress of mental 
development. There would doubtless be also a considerable 
variation in the gametes contributed by the feeble-minded person. 
Some of the combinations of germ cells might be expected to 
produce a much better mental inheritance than others. Add to 
the congenital differences thus arising, other changes due to 
intra-uterine influence, circumstances affecting early childhood, 
and various other environmental factors, and we would get a 
varied group whose individual members would be classed as 
feeble-minded or normal, in proportions varying according to the 
standard of the person making the classification and the correct- 
ness of his judgment of the persons passed upon. Naturally the 
categories found could be interpreted as resulting either from the 
mating DRXRR or, in case all the offspring were considered 
normal, from DD XRR, the normal parent being designated after 
the usual fashion as DD or DR according to whatever assumption 
is necessary to bring the facts into accord with the theory. It is 
practically impossible to determine that a person is a DR unless 
one of his immediate parents isan RR. The presence of RR’s in 
