le," but their capacity for
existence is influenced by conditions of the external world; this
renders necessary the process of adaptation. In fact, in the
differentiation of somatic from reproductive cells, material was
provided upon which natural selection could operate to shorten or
to lengthen the life of the individual in accordance with the
needs of the species. The soma is in a sense "a secondary
appendage of the real bearer of life--the reproductive cells." The
somatic cells probably lost their immortal qualities, on this
immortality becoming useless to the species. Their mortality may
have been a mere consequence of their differentiation (loc. cit.,
p. 140), itself due to natural selection. "Natural death was
not," in fact, "introduced from absolute intrinsic necessity
inherent in the nature of living matter, but on grounds of
utility,

[1] Biological Memoirs, p. 142.

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that is from necessities which sprang up, not from the general
conditions of life, but from those special conditions which
dominate the life of multicellular organisms."

On the inherent immortality of life, Weismann finally states:
"Reproduction is, in truth, an essential attribute of living
matter, just as the growth which gives rise to it.... Life is
continuous, and not periodically interrupted: ever since its
first appearance upon the Earth in the lowest organism, it has
continued without break; the forms in which it is manifest have
alone undergone change. Every individual alive today--even the
highest--is to be derived in an unbroken line from the first and
lowest forms." [1]

At the present day the view is very prevalent that the soma of
higher organisms is, in a sense, but the carrier for a period of
the immortal reproductive cells (Ray Lankester)[2]--an appendage
due to adaptation, concerned in their supply, protection, and
transmission. And whether we regard the time-limit of its
functions as due to external constraints, recurrently acting till
their effects become hereditary, or to variations more directly
of internal origin, encouraged by natural selection, we see in
old age and death phenomena ultimately brought about in obedience
to the action of an environment. These are not inherent in the
properties of living matter. But, in spite

[1] Loc. cit., p. 159

[2] Geddes and Thomson, The Evolution of Sex, chap. xviii.

85

of its mortality, the body remains a striking manifestation of
the progressiveness of the organ