Letters, Extracts, and Notes. 
753 
1921 .] 
variety must revert, and that such a process is in strict 
accord with Mendel's theory." 
The word “recessive" implies that “dominant" is used 
not in its general, but in its technical Mendelian sense. We 
suppose that “ mutationist ” means here a student of 
Mendel's principles of heredity, and such a one might be 
surprised at the views imputed to him. 
The appearance of certain characters in the Mendelian 
ratio is not a theory, but a law demonstrated by experiment, 
and the “Mendelian Law" simply means that such characters 
will appear in definite proportions in each generation. 
If we suppose that characters which appeared under 
domestication are recessive, when the domesticated forms 
interbreed with the wild stock, even if the recessives are so 
strictly weeded out by natural selection that they never 
survive to breed, still a certain number of recessives will 
infallibly appear whenever two heterozygotes interbreed. 
This, and not necessarily Colonel Meinertzhagen's assump¬ 
tion, is what is in strict accordance with Mendel’s Law. 
Cases in nature are probably never so simple as this hypo¬ 
thetical one. For instance, recent work on Lepidoptera 
suggests that in certain cases the recessives are better able 
to survive than the dominants. 
From the last paragraph on p. 530, and the second para¬ 
graph on p. 532, we are led to believe that Colonel 
Meinertzhagen considers breeding experiments to be of 
little use in the study of evolution. Yet on p. 535 he 
notices with approval Kammerer’s well-known experiments 
on Ampliibia, from which u it would appear that acquired 
characters are indeed heritable." Modern biologists, while 
acknowledging the interest and significance of Kammerer's 
results, would perhaps hardly commit themselves yet to 
such a final assertion on the Homeric Question in biology. 
Further, there is every reason to believe that Mendel's 
Law holds for animals in a natural state. Take, for ex¬ 
ample, Lang's experiments on Helix nemoralis described by 
Darbishire (Journ. of Conchology, 1905). Some remarks 
by the latter (Introduction to a Biology, 1917, pp. 217-219) 
on the normal and abnormal in inheritance also answer 
