[1] The _Descent of Man._
96
of generations of somatic cells which can succeed one another in
the course of a single life, and furthermore the number as well
as the duration of each single cell-generation is predestined in
the germ itself."[1]
Only in the vague conception of a harmonising or formative
structural influence derived from the germ, perishing in each
cell from internal causes, but handed from cell to cell till the
formative influence itself degrades into molecular discords, does
it seem possible to form any physical representation of the
successive events of life. The degradation of the molecular
formative influence might be supposed involved in its frequent
transference according to some such dynamic actions as occur in
inanimate nature. Thus, ultimately, to the waste within the cell,
to the presence of a force retardative of its perpetual harmonic
motions, the death of the individual is to be ascribed. Perhaps
in protoplasmic waste the existence of a universal death should
be recognised. It is here we seem to touch inanimate nature; and
we are led back to a former conclusion that the organism in its
unconstrained state is to be regarded as a contrivance for
evading the dynamic tendencies of actions in which lifeless
matter participates.[2]
[1] Weismann, _Life and Death; Biological Memoirs_, p. 146.
[2] In connection with the predestinating power and possible
complexity of the germ, it is instructive to reflect on the very
great molecular population of even the smallest spores—giving
rise to very simple forms. Thus, the spores of the unicellular
Schizomycetes are estimated to dimensions as low as 1/10,000 of a
millimetre in diameter (Cornil et Babes, _Les Batteries_, 1. 37).
From Lord Kelvin's estimate of the number of molecules in water,
comprised within the length of a wave-length of yellow light
(_The Size of Atoms_, Proc. R. I., vol. x., p. 185) it is
probable that such spores contain some 500,000 molecules, while
one hundred molecules range along a diameter.
97
THE NUMERICAL ABUNDANCE OF LIFE
We began by seeking in various manifestations of life a dynamic
principle sufficiently comprehensive to embrace its very various
phenomena. This, to all appearance, found, we have been led to
regard life, to a great extent, as a periodic dynamic phenomenon.
Fundamentally, in that characteristic of the contrivance, which
leads it to respond favourably to transfer of energy, its
enormous extension is due. It is probable that to its instability
its numerical abundance is to be traced—for this, necessitating
the continual supply of all the parts already formed, renders
large, undifferentiated growth, incompatible with the limited
supplies of the environment. These are fundamental conditions of
abundant life upon the Earth.
Although we recognise in the instability of living systems the
underlying reason for their numerical abundance, secondary
evolutionary causes are at work. The most important of these is
the self-favouring nature of the phenomenon of reproduction. Thus
there is a tendency not only to favour reproductiveness, but
early reproductiveness, in the form of one prolific
reproductive.