ese 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.

XV. THE VALUE OF COLOUR IN THE STRUGGLE FOR LIFE. By E.B. Poulton.

Hope Professor of Zoology in the University of Oxford.

INTRODUCTION.

The following pages have been written almost entirely from the
historical stand-point. Their principal object has been to give some
account of the impressions produced on the mind of Darwin and his great
compeer Wallace by various difficult problems suggested by the colours
of living nature. In order to render the brief summary of Darwin's
thoughts and opinions on the subject in any way complete, it was found
necessary to say again much that has often been said before. No attempt
has been made to displ