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I50 DESIGN IN NATURE<br />
spermatozoon or male element ; that presented by the ovule or female element ; and by the anthers, elaters, and<br />
other parts connected with reproduction. Plants display in a marked degree the globular, concentric, radiatmg,<br />
branched, segmented, and spiral arrangements to which I have so strongly directed attention in the present<br />
connection.<br />
The history of the reproductive elements is virtually that of the cell : indeed, to understand the former it is<br />
necessary to consider the latter.<br />
A few additional observations regarding the cell from the reproductive point of view will be useful. While the<br />
cell may, for practical purposes, be taken as the structural unit for plants and animals, it would be a mistake to<br />
regard it as in any way simple. Each cell and each group of cells display pecuHarities, and are characterised by<br />
features of their own. There is, strictly speaking, no such thing as absolutely simple, identical, homogeneous<br />
organic matter.<br />
This seems proved in two ways :<br />
when dead.<br />
(a) by its behaviour while hving ; and<br />
(b) by the appearance presented by it<br />
Living matter takes in and gives out inorganic matter : it grows, runs a given course, divides, and repro-<br />
duces itself.<br />
Dead organic matter when subjected to the action of powerful stains, in the majority of cases reveals traces<br />
of differentiation and structure.<br />
Even protoplasm presents a reticulated appearance and consists of four or more elements, namely, oxygen,<br />
hydrogen, nitrogen, and carbon, with small quantities of sulphur and other ingredients.<br />
Living matter as seen in cells, cell plants and cell animals, the reproductive elements, &c., presents under high<br />
powers of the microscope a great variety of forms— globular, concentric, radiating, branched, segmented, spiral,<br />
reticulated, and otherwise.<br />
The cell has a career and history of its own. It cannot be regarded as homogeneous, as it is composed of<br />
a cell wall, protoplasm or cell contents, a nucleus, and, generally, one or more nucleoh. In addition to these are<br />
to be noted, in many instances, plastids, an attraction-sphere mth centrosome, vacuoles, metaplasm, chromatin-<br />
network, linin-network, net knot (Karyosome), &c.<br />
The nucleus is, in many cases, a highly complex structure, and runs through many changes which involve<br />
differentiation of a kind.<br />
The changes referred to are generally classed under the term Mitosis (from a thread), and include indirect division<br />
of the nucleus involving (a) the formation of an amphiaster ; (b) conversion of the chromatin into a thread (spirem) ;<br />
(c) segmentation of the thread into chromosomes ;<br />
(d) splitting of the chromosomes, &c. (Flemming, 1882.)<br />
The cell plants and animals generally display a nucleus, with or without nucleoU, a contractile vesicle, one or<br />
more vacuoles, food spaces, &c.<br />
The reproductive elements—male and female—on which so much depends, are separate and independent entities.<br />
They pass through quite a compUcated series of phases before they reach maturity, and when they do reach that<br />
state and unite and amalgamate in the act of impregnation, they inaugurate, as already stated, a progressive series<br />
of extraordinary and even starthng changes, characterised by cleavages, reunions, intricate processes of weaving,<br />
of tissue forming, of organ forming, of modelhng, &c.<br />
All this, it need scarcely be added, makes for differentiation, division of labour, and heterogeneity.<br />
To Schleiden and Schwann, as already indicated, belongs the great merit of first directing attention to the cell<br />
as the fundamental factor in plants and animals. These investigators announced the cell theory in 1838, and this<br />
date marks a new and important era in anatomy and physiology. The cell, as a matter of fact, is itself composed<br />
of molecules, and the molecules of atoms ; and it is, strictly speaking, in the atoms and molecules that we nmst<br />
search for those properties, peculiarities, and powers which distinguish one cell from another, one plant from<br />
another, and one animal from another. To the same source are to be traced the fundamental differences in the<br />
sexual elements which determine lineage and transmission by descent. In the atoms and molecules of the cells<br />
and sexual elements are stored up, in a potential form, all the properties, peculiarities, and powers which charac-<br />
terise the parent or parents physically and mentally. When it is stated that the atoms and molecules of cells are,<br />
primarily, the parents of plants and animals, it is not meant that the cells to which they give origin contain in<br />
miniature all the parts of future plants and animals. They merely contain, in a latent form, the initiatory matter,<br />
which, under guidance and hereditary laws, develops in favourable conditions of food, heat, light, moisture &c.<br />
into plants and animals which in all respects resemble their ancestors.<br />
No provision is made for variations or the perpetuation of variations, which are calculated to introduce<br />
confusion, and to subvert or destroy originally created types. When variations do occur, they are, as a. rule, speedily<br />
eliminated. Neither is provision made for the introduction of acquired physical and mental peculiarities. In