Sex
The law of physical life
It is a universal rule of physical life that every individual being
undergoes a development which we know as its individual life and
which, so far as its physical substance is concerned, ends with death. Death is the destruction of the greater part of this individual organism which, when death ensues, once more becomes lifeless matter. Only small portions of this matter, the germ cells, continue to live under certain conditions which nature has fixed.
The germ cell—as has been established by the microscope—is the tiny
cell which in the lowest living organisms as well as in man himself, forms the unit of physical development. Yet even this tiny cell is already a highly organized and perfected thing. It is composed of the most widely differing elements which, taken together, form the so-called protoplasm or cellular substance. And for all life established in nature the cell remains the constant and unchanging form element. It comprises the cell-protoplasm and a nucleus imbedded in it whose substance is known as the nucleoplasm. The nucleus is the more important of the two and, so to say, governs the life of the cell-protoplasm.
The lower one-celled organisms in nature increase by division, just as
do the individual cells of a more highly organized, many-celled order
of living beings. And in all cases, though death or destruction of the
cells is synonymous with the death or destruction of the living
organism, the latter in most cases already has recreated itself by
reproduction.
We will not go into the very complicated details of the actual process
of the growth and division of the protoplasmic cells. It is enough to
say that in the case of living creatures provided with more
complicated organisms, such as the higher plants, animals and man, the
little cell units divide and grow as they do in the case of the lower
organisms. The fact is one which shows the intimate inner relationship
of all living beings.
The ladder of organic ascent
As we mount the ascending ladder of plant and animal life the
unit-cell of the lower organisms is replaced by a great number of
individual cells, which have grown together to form a completed whole. In this complete whole the cells, in accordance with the specific purpose for which they are intended, all have a different form and a different chemical composition. Thus it is that in the case of the plants leaves, flowers, buds, bark, branches and stems are formed, and in that of animals skin, intestines, glands, blood, muscles, nerves, brain and the organs of sense. In spite of the complicated nature of numerous organisms we find that many of them still possess the power of reproducing themselves by division or a process of "budding." In the case of certain plants and animals, cell-groups grow together into a so-called "bud," which later detaches itself from the parent body and forms a new individual living organism, as in the case of the polyps or the tubers in plant life.
A tree, for instance, may be grown from a graft which has been cut off
and planted in the ground. And ants and bees which have not been
fecundated are quite capable of laying eggs out of which develop
perfect, well-formed descendants. This last process is called
parthenogenesis. It is a process, however, which if carried on through
several generations, ends in deterioration and degeneracy. In the case
of the higher animals, vertebrates and man, such reproduction is an
impossibility.
These higher types of animal life have been provided by nature with
special organs of reproduction and reproductive glands whose
secretions, when they are projected from the body under certain
conditions, reproduce themselves, and increase and develop in such
wise that the living organism from which they proceed is reproduced in
practically its identical form. Thus it perpetuates the original type. Philosophically it may be said that these cells directly continue the life of the parents, so that death in reality only destroys a part of the individual. Every individual lives again in his offspring.