Note 74 — II THE BASIS OF THE POPULATION PROBLEM: (1) THE QUANTITATIVE ASPECT

Among many plants and not infrequently among lower animals the sexes are not separate—both male and female generative organs being found on the same individual. This condition occurs in some fish, though examples of hermaphroditism are rare in the Vertebrates. As a general rule in such cases the two generative organs found in the same individual ripen at different times and cross-fertilization is effected. In such cases the description given above applies. Where self-fertilization occurs, the above account does not apply in detail; the occurrence of self-fertilization, however, in no way invalidates the general conclusions that will be drawn in what follows.