In the female sex the first stage of the development of gametes is similar to that found in spermatogenesis – the oogonia—the cells eventually giving rise to the eggs— undergo proliferation by mitotic divisions. They then become oocytes and enter a period of growth. Owing to the fact that the egg contributes the greater part of the substances used in [...]
The development of the spermatozoa takes place in the male gonads, the testes. In vertebrates and insects, the testes are composite organs consisting of numerous seminiferous tubules, or seminiferous lobules, converging toward common ducts which lead the mature sperm to the exterior. Spermatogenesis is a continuous process, and various stages of development of the sperm may be observed in the [...]
As the oocyte grows and as various inclusions are produced in its cytoplasm, a pattern of organization gradually emerges, which will be of importance when the eggs start developing. The arrangement of various substances and cellular constituents in the advanced oocyte and, later, in the egg shows a polarity, that is, an unequal distribution with respect to what may be [...]