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VARIATION 201

ments, but as activity increased and brains grew, the power of
varying actions to fit varying requirements became consider-
able.³' ** As fast as essential faculties multiply, and as fast
as the number of organs which co-operate in any given
function increases, indirect equilibration through natural
selection becomes less and less capable of producing specific
adaptations; and remains capable only of maintaining the
general fitness of constitution to conditions. The production
of adaptations by direct equilibration then takes the first
place : indirect equilibration serving to facilitate it. Until at
length, among the civilised human races, the equilibration
becomes mainly direct: the action of natural selection being
limited to the destruction of those who are too feeble to live,
even with external aid."

Returning to our scheme of Originative and Direct-
ive Factors, let us inquire into Spencer's views re-
garding Variation and Selection.

Spencer recognised three causes of variation. First
there is heterogeneity among progenitors which
"generates new deviations by composition of forces " ;
in other words new patterns arise from the mingling
of diverse hereditary contributions in fertilisation.
Secondly, functional variation in the parents produces
unlikeness in the offspring; those begotten under
different constitutional states are different. In other
words, fluctuations of nutrition in the parental body
may cause variations in the germ-plasm. [In mammals
there are also modifications produced during the pre-
natal life of the offspring which are congenital in the
sense that they are present at birth in latent or patent
form, which do not, however, really affect the germ-
plasm since they disappear in the third generation.]
Thirdly, an organism exposed to a marked change of
external conditions, may have its equilibrium altered,
and the offspring maybe influenced. " The larger



	VARIATION 201 ments, but as activity increased and brains grew, the power of varying actions to fit varying requirements became consider- able.³' ** As fast as essential faculties multiply, and as fast as the number of organs which co-operate in any given function increases, indirect equilibration through natural selection becomes less and less capable of producing specific adaptations; and remains capable only of maintaining the general fitness of constitution to conditions. The production of adaptations by direct equilibration then takes the first place : indirect equilibration serving to facilitate it. Until at length, among the civilised human races, the equilibration becomes mainly direct: the action of natural selection being limited to the destruction of those who are too feeble to live, even with external aid." Returning to our scheme of Originative and Direct- ive Factors, let us inquire into Spencer's views re- garding Variation and Selection. Spencer recognised three causes of variation. First there is heterogeneity among progenitors which "generates new deviations by composition of forces " ; in other words new patterns arise from the mingling of diverse hereditary contributions in fertilisation. Secondly, functional variation in the parents produces unlikeness in the offspring; those begotten under different constitutional states are different. In other words, fluctuations of nutrition in the parental body may cause variations in the germ-plasm. [In mammals there are also modifications produced during the pre- natal life of the offspring which are congenital in the sense that they are present at birth in latent or patent form, which do not, however, really affect the germ- plasm since they disappear in the third generation.] Thirdly, an organism exposed to a marked change of external conditions, may have its equilibrium altered, and the offspring maybe influenced. " The larger