During the growth of the oocyte not only does the amount of cytoplasm increase in quantity, but it changes in quality by the elaboration and regular distribution of various cell inclusions and specially modified parts of the cytoplasm which, are essential for the development of the embryo. In most animals which have been investigated with modern methods, young oocytes show [...]
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 [...]
The cytoplasm of the egg, and particularly its cortex, starts the chain of reactions which eventually leads to the differentiation of parts of the embryo, it should not be assumed that the structure of the future embryo is rigidly determined by local differences in the cytoplasm of the egg. The local peculiarities of the egg cytoplasm are only some of [...]