160 HERBERT SPENCER

posed to be grouped together in ids, each of which
is supposed to possess a complete complement of the
specific characters of the organism and also to have an
individual character. The ids are arranged in linear
series to form the visible idants or chromosomes,
which will be slightly different from one another
according to the individualities of the component ids.
When the fertilised egg-cell develops, it gives rise

(1) to somatic cells which carry with them part of the
germ-plasm, and differentiate to form the body, and

(2) to the germ cells which reserve part of the germ-
plasm in an unchanged state, and eventually give
rise in appropriate conditions to new individuals and
their germ-cells.

Spencer refused to accept the contrast between
forfp-cells and germ-cells as expressing a fact, and
referred for his reasons to the numerous cases in
which small pieces of a plant or polyp may grow
into an entire organism. But when he represented
Weismann as maintaining that the " soma contains
in its components none of those latent powers
possessed by those of the germ-plasm," he did not
do justice to the comprehensive theory of the " Germ-
plasm." For Weismann assumes that in certain
cases the body-cells, even though differentiated, may
carry with them some residual unused-up germ-plasm.

When a lizard regrows a lost tail—effectively
responding to a casualty which has been common
for untold generations—Weismann interprets the
mechanism of this as due to a reserve of tail-deter-
minants resident at or near the place of breakage,
and localised there as the result of a long-continued
process of selection. A chamaeleon does not re-eterminants are sup-borate organic crystallisa-tific and trans-s intrinsic incoherence; worthless as