The Mystery of Sex, or Sex Polarity

...separating from one another, regain their full structural organization before starting to divide again in the typical way.”

The following passage quotes Patrick Geddes (1854–1932), a Scottish biologist who studied the evolution of sex. Geddes says: “Sometimes as many as three or four spores of simple Algae join together, as if they are gathering enough momentum to begin life together. The young forms of the sun-animalcule original: "sun-animalcule"; a microscopic, single-celled organism with radiating spines usually unite in pairs, but the scientist Gabriel has observed cases where several join together. In another species of sun-animalcule, anywhere from two to thirty individuals may join loosely in what is called plastogamy the fusion of the cell bodies without the fusion of their nuclei, though the actual union of nuclei occurs only between two individuals. Similarly, in gregarines parasitic organisms often found in the guts of insects, while they usually unite in pairs, the researcher Gruber has observed what might be called multiple conjugation the process by which two microorganisms exchange genetic material. ... The conjugation of two similar single-celled organisms occurs, as we have seen, very generally in the Protozoa, and is also a common fact in the life history of simple Algae. ... Facing cells in neighboring strands are attracted to one another, and the contents of one cell move entirely into the other. In the vast majority of cases where conjugation occurs, the joining cells appear to be identical, but we must remember that it does not necessarily follow that they are functionally alike. ... In fertilization among higher plants and animals, the two elements that unite are highly specialized, both in how they differ from each other and how they differ from the general cells of the body. A study of these phenomena in loose protist a diverse group of single-celled organisms colonies, which suggest a bridge between single-celled and multi-celled organisms, shows how gradually this latter contrast may have developed.”

As the scale of life ascends under the drive of evolution, life forms begin to develop organs through which sexual activities can be better performed. In some cases, individuals are clearly separated into male and female in their sexual roles, even if they look similar on the outside. In other cases, each individual possesses the organs of both sexes, a state known as Hermaphroditism the condition of having both male and female reproductive organs. This state is quite common among some of the lower forms of living things. It is found in the oyster and other shellfish, barnacles and related forms, the tapeworm, the earthworm, and even the...