On the Spermatogenesis of the Louse (Pediculus corporis and P. capitis), with some Observations on the Maturation of the Egg

Abstract

The main facts of the spermatogenesis have been given in Section 3 A above. The most important points are as follows: (1) The somatic chromosome number of both sexes is twelve, but spermatogonial mitotic figures show only six. There is some evidence that these are double, and we ascribe the existence of the apparently haploid number in the spermatogonia to premature pairing. (2) There is only one spermatocyte division, which is extremely unequal, leading to the separation of a minute polar-body-like cell which degenerates. (3) The centrosome of the spermatid is double, and from each half an axial filament grows out, so that the developing spermatozoa have two conspicuous axial filaments. (4) The development of the mitochondrial body is described. (5) The acrosome is derived from a deeply staining body which appears in the spermatocyte and becomes applied to the nucleus of the spermatid like a cap. (6) The existence of a deeply stained rod, of unknown origin and fate, in the growing oöcyte, and of a posterior mass of stained granules in the mature egg, is shortly referred to. The egg nucleus undergoes two polar divisions, and fertilisation appears to be essential if the egg is to develop. (7) Breeding experiments did not confirm Hindle's observation that broods consisting only of males or only of females are frequent. Some broods with great preponderance of one or the other sex were obtained.