CHAPTER V

Sex in Animal Life

In animal life, just as in plant life, we find male and female elements of reproduction. In animals, the male reproductive element is called the spermatozoon; the female reproductive element is called the ovum original: "Spermatozoon" and "Ovum"; Latin terms for "seed-animal" and "egg".

The spermatozoa (the plural of spermatozoon) are the active, moving parts of the male reproductive element. They consist of a head, a rod-shaped middle section, and a long, hair-like tail. They move in a spiral pattern through the vibrating motion of this tail. These were formerly thought to be parasites living in the seminal fluid, but researchers eventually discovered they are actually the fecundating cell original: "fecundating cell"; the cell responsible for fertilization or male element of reproduction. They are found in all animals, including humans.

The size of spermatozoa varies between different species. In humans, they are about one six-hundredth of an inch long. Their unique movements look like those of a tadpole, with the hair-like tail moving constantly from side to side to push the spermatozoon from one point to another. It is made of protoplasm, the substance that forms the basis of all physical life In the 19th and early 20th centuries, protoplasm was considered the "physical basis of life," a term popularized by Thomas Henry Huxley. Spermatozoa develop from a "mother-sperm-cell" through a process of segmentation the division of a cell into smaller parts or subdivision, in a manner similar to that of the simplest forms of animal life. They live in a jelly-like original: "gelatinous" fluid that mixes with other fluids produced by glands to make up the male seminal fluid.

Geddes Patrick Geddes (1854–1932) was a prominent biologist and sociologist who co-authored "The Evolution of Sex" provides the following information regarding the physiology of spermatozoa. He says:

"A few facts about the physiology of sperm require attention: (a) It is specialized as a highly active cell. Its tiny size, the typical lack of any burdening original: "encumbering" nourishing material, the ability of the tail to move and contract, and its general shape all make it suited for..."