The discovery of De Vries, that new species may arise by mutation and
the wide if not universal applicability of Mendel's Law to phenomena of
heredity, as shown especially by Bateson and his pupils, must, for
the time being, if not permanently, serve as a basis for theories of
evolution. These discoveries place before the experimental biologist the
definite task of producing mutations by physico-chemical means. It
is true that certain authors claim to have succeeded in this, but
the writer wishes to apologise to these authors for his inability to
convince himself of the validity of their claims at the present moment.
He thinks that only continued breeding of these apparent mutants through
several generations can afford convincing evidence that we are here
dealing with mutants rather than with merely pathological variations.
What was said in regard to the production of new species by
physico-chemical means may be repeated with still more justification
in regard to the second problem of transformation, namely the making
of living from inanimate matter. The purely morphological imitations
of bacteria or cells which physicists have now and then proclaimed as
artificially produced living beings; or the plays on words by which,
e.g. the regeneration of broken crystals and the regeneration of lost
limbs by a crustacean were declared identical, will not appeal to the
biologist. We know that growth and development in animals and plants are
determined by definite although complicated series of catenary chemical
reactions, which result in the synthesis of a DEFINITE compound or group
of compounds, namely, NUCLEINS.
The nucleins have the peculiarity of acting as ferments or enzymes
for their own synthesis. Thus a given type of nucleus will continue to
synthesise other nuclein of its own kind. This determines the continuity
of a species; since each species has, probably, its own specific nuclein
or nuclear material. But it also shows us that whoever claims to have
succeeded in making living matter from inanimate will have to prove that
he has succeeded in producing nuclein material which acts as a ferment
for its own synthesis and thus reproduces itself. Nobody has thus far
succeeded in this, although nothing warrants us in taking it for granted
that this task is beyond the power of science.