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SH DESIGN IN NATURE<br />
Mr. (afterwards Mr. Justice) Grove, in his admirable work on the " Correlation of the Physical Forces," thus<br />
puts it : " All matter, as far as we can ascertain, is ever in movement, not merely in masses, as with the planetary<br />
spheres, but also molecularly, or throughout its most intimate structure. . . . Matter and force are correlates m the<br />
strictest sense of the word ;<br />
Fig. 63. JJrosera rotundifolia. Diagi'ani of<br />
the same cell of a tentacle, showing the various<br />
foi-ms (A, B, C, D, E, F, G, H) siicoessively assumed<br />
by the aggregated masses of protoplasm<br />
(Darwin).<br />
the conception of the existence of the one involves the conception of the existence<br />
of the other ; the quantity of matter, again, and the degree of force, involve conceptions of space and time. ...<br />
force which<br />
Motion will directly produce heat ; and electricity, being produced by it, wiU produce magnetism—a<br />
is always developed by electrical currents at right angles to the direction of those currents. . . . Pliicker has recently<br />
succeeded in showing that crystalhne bodies are definitely affected by magnetism, and take a position in relation to<br />
. . The same principles and<br />
.<br />
and<br />
the lines of magnetic force dependent upon their optical axis or axis of symmetry.<br />
mode of reasoning might be appHed to the organic as well as the inorganic ;<br />
&c., might, and at some time will, be shown to have similar definite correlations. . . . From<br />
force, animal and vegetable heat,<br />
Professor Matteucci's<br />
experiments it appears that whatever mode of force it be which is propagated along the nervous filaments, this<br />
mode of force is definitely affected by currents of electricity."<br />
From the foregoing it will be evident that motion is a characteristic of all bodies, animate and inanimate. It<br />
will therefore occasion no surprise if I lay it down as an axiom that the most rudimentary plants and animals move<br />
in all their particles and parts, and that what is true of the lowest plants and animals is equally true of the highest.<br />
®<br />
Fig. 64. Drosera rotundifolia. Diagram of<br />
the same cell of a tentacle, showing the various<br />
forms (1, 2, 3, 4, 6, 6, 7, 8) successively assumed<br />
by the aggregated masses of protoplasm (Darwin).<br />
Everything that lives grows and has a hfe history, and the fundamental<br />
feature of growth is movement. Movement is essentially of two kinds.<br />
There is a movement of the atoms and molecules primarily concerned in<br />
growth and development, which, being unseen, is to be regarded as<br />
invisible movement, that is, movement not recognisable by the unaided<br />
eye ; and<br />
there is a movement of plants and animals, and parts thereof,<br />
which, being seen, with or without the microscope, may not inaptly be<br />
designated visible motion. It is the latter form of motion I propose to<br />
discuss here. The difference between visible and invisible motion may<br />
be explained as follows. When motion ceases to be visible, that is, when<br />
moving masses strike against each other and apparently stand still, motion<br />
is re-developed in the shape of heat, which is invisible motion. In the<br />
steam-engine, for example, the piston and all its concomitant masses of<br />
matter are moved by the molecular dilatation of the vapour of the water,<br />
the movement of the molecules being imperceptible. If homogeneous<br />
substances come together, heat alone is generated ; but if homogeneous<br />
and heterogeneous substances come together, electricity is produced ;<br />
some have thought that, whereas the contents of vegetable cells are<br />
heterogeneous, and the saps presented to them are nearly if not quite<br />
homogeneous, electricity takes part in the circulation in plants.<br />
The microscope becomes a necessity when deaHng with minute masses of living matter such as are met with in<br />
protoplasm, cells, tissues, low vegetable and animal forms, &c.<br />
Darwin has described and figured vegetable protoplasm moving and assuming a great variety of shapes.^<br />
Thus, when speaking of the aggregation of the cell contents of the glands and tenacles of Drosera rotundifolia, he<br />
says : " By whatever cause the process may have been excited, it commences within the glands, and then travels<br />
down the tentacles. It can be observed much more distinctly in the upper cells of the pedicels than within the<br />
glands, as these are somewhat opaque. The httle masses of aggregated matter are of the most diversified shapes,<br />
often spherical or oval, sometimes much elongated, or quite irregular, with thread or necklace-Uke or club-formed<br />
projections. They consist of thick, apparently viscid matter, which in the exterior tentacles is of a purplish, and<br />
in the short discal tentacles of a greenish, colour. These little masses incessantly change their forms and positions,<br />
being never at rest. A single mass will often separate into two, which afterwards reimite. Their movements are<br />
rather slow, and resemble those of amoebae or of the white corpuscles of the blood. We may, therefore, conclude<br />
that they consist of protoplasm. If their shapes are sketched at intervals of a few minutes, they are invariably seen<br />
to have undergone great changes of form ; and the same cell has been observed for several hours. Eight rude,<br />
though accurate sketches of the same cell, made at intervals of two minutes or three minutes illustrate some<br />
of the simpler and commonest changes (Fig. 6-3).<br />
" The cell A, when first sketched, included two oval masses of purple protoplasm touching each other. These<br />
became separate, as shown at B, and then re-united, as at C. After the next interval a very common appearance<br />
' "Insectivorous Plants," by Charles Darwin, M.A., F.R.S., &(;. London, 1875, pp. 39 to 42.<br />
and