THE ORIGIN OF SEX
That part of human life and living that is associated with the functions of sex and reproduction is at once the cause of the world's greatest misery and the world's greatest happiness. It is the subject of the greatest popular ignorance and superstition, and at the same time the field of the most wonderful of all scientific knowledge.
For the origin of sex we must look back into the remote ages of creation in the early stages of organic evolution.
Fundamental function of the cell
The first essential property of matter that makes life possible is the power of nutrition, which means the ability of the living cell to transform other chemical substances into its own protoplasm or living substances.
But this world would have remained a barren mass of igneous rock if nutrition had been the only function with which the earlier forms of life were endowed. Not only must the living cell be enabled to grow by absorbing other substances, but it must reproduce itself, or multiply the number of living individuals.
First form of reproduction
The first method by which this was accomplished was undoubtedly one of simple division; that is, the living cell grew by absorbing other substances and when sufficient size had been attained, divided, forming two daughter-cells. This division process of reproduction is the form by which all bacteria (so-called dis-ease germs) and many other lower forms of life increase their numbers.
Second form of reproduction
Strength in fusion of cells
This process of reproduction, by simple division, was early supplemented by another process of reproduction in which two living cells first fused or combined and then divided to form two or more daughter-cells. This form of reproduction seems to have added stimulus or vitality to the organisms. The supposed reason for this is that the isolated cell was inclined to weaken or lose its chemical balance or tone. The exact nature of this deterioration is not very clearly understood, but in a higher form of life it is well illustrated by the tendency of certain plants to "run out" when grown continually in the same soil, or of animals to become weakened when inbred. At least, all scientists concede that with the process of fusion or the combining of two cells there is added a stimulating and invigorating force which enables life to combat more successfully the unfavorable elements of its environment, and to change or evolve into higher forms.
Sexual reproduction in plants
Throughout the range of plant and animal life this process of cell union, or sexual reproduction, has grown and become elaborated into most varied and wonderful forms. Large volumes could be written describing the many wonderful adaptations of plant and animal life, the purpose of which is to secure sexual reproduction. All those who have studied botany are familiar with the many ways in which the seeds of plants are fertilized by pollen. For instance, certain species of orchids have a receptacle in the blossom, shaped like a teapot, which is filled with a fluid resembling water. This little teapot has an entrance and an exit. Near the entrance is sweet-scented nectar which attracts the bee. Fertilization of orchids As the bee passes through this gateway he is tripped up on a little trap-door arrangement and precipitated into the fluid. His wings having become wet, he is obliged to crawl out through the exit.
The wonderful process of flower fertilization
The object of this elaborate device is as follows: In the entrance passageway is located the stigma (female organ), while in the exit passageway the male or pollen-bearing organ of the orchid is found. The bee visits several of these flowers consecutively, and, as he makes his exit from each flower, he bears away on his body a portion of the pollen, which is transferred to the stigma of the next flower visited; while the bee, being forced to go through a "plunge bath" before visiting another flower, acquires a fresh load of pollen in each case. This scheme is a certain means of securing fertilization or sexual reproduction, and positively prevents inbreeding (the fertilization of a flower by its own pollen). This is merely one of the wonderful adaptations of nature in the solution of the sex problem.
Reproduction among fishes
In the animal kingdom the methods of sexual reproduction are also varied and wonderful. In many of the lower forms of animals, such as the various sea-creatures, the methods of reproduction may be those of division, as first mentioned, or a method combining division with true sexual reproduction. In the case of fishes, the eggs of the female are deposited in the bottom of a stream and are later fertilized by the sperm-cells of the male fishes. This involves a tremendous waste of reproductive cells, scarcely less extravagant than the waste of pollen in plants, such as is seen in a corn-field when Nature's wasteful methodsthe ground becomes yellow, during the tasseling season, with the myriads of pollen grains that failed to secure lodgment upon the silks of the young ears of corn.
Reproduction in higher forms of life
In the types of animals that are of higher form than fishes, that is, reptiles, birds, and mammals, the fertilization of the germ-cell (egg) takes place within the body of the female. In the case of the latter group—mammals—the true egg is hatched within the body of the female, and the offspring, or embryo as it is known to scientists, grows there for a considerable period before birth.