Abstract
Ovogenesis occurs throughout adult life in the guinea pig, cat, dog, and man, as a rhythmical process, during which thousands of ova are produced de novo, followed by the degeneration of all but a few which mature. In the guinea pig, cat and dog this rhythm of ovogenesis coincides with the rhythm of the oestrus cycle, beginning at ovulation and reaching its peak at anoestrum, with wholesale degeneration occurring at late prooestrum. Lack of knowledge of a definite oestrus cycle in man weakens the correlation here, but the rhythm of ovogenesis is as striking in the number of ova produced and destroyed as in the other animals.
New sex cells are produced by proliferations from the germinal epithelium in the form of invaginations and ingrowths of epithelial cords. These become separated from the germinal epithelium, pass through the tunica albuginea and form a more or less continuous layer underneath the tunica. From one to many cells in each group may develop into ova, the remainder forming the follicle cells.
Contrary to the concept involved in the germ plasm theory, the mammalian ova (excepting those that mature and are fertilized) have a shorter life span than any other group of cells in the body outside of the reproductive tract.
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