BELIEFS
particular purposes, the results of evolution are more signifi-
cant than the mechanism by which those results were
achieved. In regard to this mechanism, the evidence avail-
able seems to point to the conclusion that mutation, hybrid-
ization, retardation of growth and fcetalization (which are
themselves the products of mutation), arid natural selection
are sufficient to account for evolutionary change and that
it is unnecessary to invoke such concepts as orthogenesis
or the inheritance of acquired characters. Lamarckism has
often been supported by those who are anxious to vindicate
the pre-eminence of mind in the world. But, as Haldane
has pointed out, these crusaders are really doing a dis-
service to their cause. If characters acquired as, the result
of more or less intelligently directed effort are inherited,
then we should expect evolution to be a rapid process. But
in fact it is extremely slow. If evolution is due to 'cunning*
rather than 'luck/ then the cunning must be of a pretty
feeble kind; for it has brought life a relatively short way
in a very long time. In fact, the evidence for Lamarckism
is extremely inadequate. (Neither Lamarckism nor the
orthogenetics theory seems to be compatible with the fact
that most mutations are demonstrably deleterious*) Mind,
as we know, can affect the body profoundly and in a great
variety of ways. But, as a matter of empirical fact, this
power of affecting the body is limited. To modify the
arrangement of the genes must be numbered, it would
seem, among the things it cannot do.
There is only one other point in regard to the mechanism
of selection about which I need speak in the present context.
Competition, when it exists, is of two kinds: between
members of different species (inter-specific) and between
members of the same species (intra-specific). Intra-specific
selection is commoner among abundant species than among
species with a small membership and plays a more important
part in their evolution. Many of the results of natural
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