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any modification which alters the quality of an organism, 
it is an admission that distinctive qualities are the product 
of some other influence. And surely all quality cannot be 
resolved into quantity without removing all the distinctive 
meaning attached to those terms. It is surely legitimate, 
for example, to treat the perfume of flowers as a quality of 
the plant. The flowers which emit no scent and the 
flowers which load the air with perfume have surely dis 
tinctive qualities. But if so, the perfume of flowers cannot 
have been produced by Natural Selection but by an inde 
pendent transforming influence. Or are we to understand 
that all modifications of structures are mere matters of 
quantity ? Such a definition seems to me to overlook 
Mr. Herbert Spencer’s distinction between growth and 
development. Growth is a mere increase of size; develop 
ment is an increase in the complexity of the structure. It 
seems to me that we should be perfectly justified in calling 
the former a quantitative and the latter a qualitative modi 
fication. But if we accept this definition, then the dictum 
of Dr. Weismann would deny to Natural Selection the 
power of producing that development without which pro 
gressive modification of structure would be impossible. 
Or does he mean to say that Natural Selection only acts 
through selecting quantitative excellence, as, for example, 
the flowers which emit the sweetest or the most penetrat 
ing perfume? But if so, some other influence, not Natural 
Selection, must have produced the perfume. 
In the preceding section of this work it has been 
shown that if we were acquainted with no special reasons 
for doubting that Natural Selection was a law of nature, 
there would still be good reason to believe that it had 
taken no part in the modification of species. The stability 
of species and the extinction of species take place apart 
from Natural Selection ; while they present especial dififi-