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372 DESIGN IN NATURE<br />
and independent in their nature. If, however, plants and animals can unaided reproduce themselves in virtue of<br />
inherent vital powers, and discharge the highest functions incidental to life, it follows that they may be credited<br />
with the power to discharge the minor functions, among which may be included the process of feeding, growing,<br />
secreting, excreting, moving, resting, &c. In other words, if plants and animals can in the absence of foreign matter,<br />
irritation, and external stimulation perform the major and higher functions of life they may be trusted to perform<br />
the minor and lower functions.<br />
Reproduction is, in all cases, essentially an atomic, molecular, vital process. It is in the atoms and molecules,<br />
or the cells formed by them, that the future being, whether plant or animal, finds its origin and source.<br />
In the higher animals, where there are male and female elements and separate sexual organs, the elements are<br />
usually contained in cells. Thus in mammals the ovum and spermatozoon are both cellular in character. In the<br />
several orders of plants, reproduction is, for the most part, effected by spores, germs, and seeds which are atomic,<br />
molecular, or cellular in character, according to circumstances. It is, however, often effected artificially by detaching<br />
and planting or grafting parts of the originals (stems, branches, leaves, &o.) in suitable localities. Plants may also<br />
reproduce themselves by means of roots, runners, bulbs, &c.<br />
It is in reproduction that heredity makes its most indelible impression. Impregnation and fecundation furnish<br />
examples of the subtlest and most permanent combinations of living matter. As we cannot see by the highest<br />
powers of the microscope the atoms, and the molecules formed by them, or analyse by the aid of any known process<br />
in chemistry those practically invisible and intangible entities, we are forced to accept results, which while they<br />
cannot be actually demonstrated, are, nevertheless, clear as inferences, deductions, and matters of reason. If from<br />
the coalescence of known molecular male and female elements plants and animals always and invariably identical<br />
are produced, it follows that in the male and female elements themselves reside or inhere the potentialities necessary<br />
to the production of the plants and animals in question. In other words, if the male and female molecular elements<br />
positively refuse to form plants and animals essentially differing from those of which they themselves are component<br />
and important parts, then it goes without saying that plants and animals, in every instance, only reproduce<br />
themselves.<br />
A fig tree cannot be obtained from a thorn ; a mammal from a reptile ; or a bird from a fish.<br />
From two wholly dissimilar male and female molecular elements such as those obtained from the several orders<br />
of plants and animals no living thing can be produced. Indeed the limits within which fructification and repro-<br />
duction are possible are exceedingly narrow. A mule and a hinny can be produced by cross breeding as between<br />
the horse and the ass, but the mule and hinny are invariably barren.<br />
The reproductive act has features in common in all classes of plants and animals. It is, however, simplest and<br />
most easily studied in the lowest forms. Here the new individual is sometimes produced by division and some-<br />
times by budding. What is virtually a protoplasmic mass simply splits into two or throws out a process or bud,<br />
which in due time becomes detached from the parent, and discharges on its own account all the functions originally<br />
discharged by the parent.<br />
In these cases only one individual and one sexual substance is required for the reproductive process. In other<br />
cases one male and one female element are contained in one and the same individual. This is the rule in herma-<br />
phrodite plants and animals. In the higher and highest plants and animals, the male and female elements are<br />
found in separate individuals. In bisexual plants and animals the male and female elements must be brought into<br />
contact either directly or indirectly, and must commingle and interpenetrate before fertilisation and reproduction<br />
can take place. Reproduction is undoubtedly an evidence of design and of life. Only living things can reproduce<br />
themselves. A crystal forms or may be formed under certain conditions, but it cannot reproduce itself after the<br />
manner of a plant or animal.<br />
It may be convenient at this stage to refer briefly to the several kinds of reproduction. The protamoeba of<br />
Professor Haeckel, one of the simplest of living forms, consists, according to him, of a minute albuminous mass. He<br />
does not explain whence came the mass or why it divides. On attaining maturity it splits into two, and in due<br />
time each half becomes as perfect as the original whole. This is the simplest possible form of reproduction. It is<br />
bisection or multiplication by division. This fundamental form of reproduction in certain cases repeats itself ; the<br />
two original halves being divided into four, the four into eight, and so on ; the parent, as it were, resolving itself into<br />
a swarm. This primary form of division is also seen in the cleavage of the impregnated human ovum. MultipU-<br />
cation by division is a vital act, and provision is made for it in the original individual. It is in no sense the result<br />
of irritation or of external stimulation.<br />
Reproduction by budding is sUghtly more complex. This is seen to advantage in cell multiplication in plants<br />
and ammals. In the buddmg process the parent sets apart and prepares a certain portion of its substance for a<br />
separate existence. In due course the separation takes place, and in such a manner that the parent is in no wise