The spermatogenesis of Hemideina thoracica White

Abstract

There is no need in prefacing this paper to emphasize the importance of Cytology in modern Biology. Nevertheless a review of the trend of this subject today may be useful to justify those parts of this work where theory appears to outstrip fact. The significance of the cell in the solution of problems of morphology and physiology was realized at the time of the promulgation of the Cell Theory. The work of the earlier cytologists, together with the findings of geneticists, later drew attention to the very great importance of the cell in studies of heredity. Now, with the facts of heredity as a threshold, modern Biology is entering upon a consideration of the part played by the cell in the Evolution of species. The treatment of this problem is still in its infancy. The first step has been taken by the initiation of the study of the changes, both permanent and temporary, of chromosome number in the individual and in the species. It is now appearing that changes in the germ plasm must underlie those changes of the individual that ultimately are the basis of Evolution - this being so, the configuration of the germ plasm in closely related species and genera merits investigation. At least insofar as it concerns itself with the germ plasm, Cytology plays an important part in the study of Organic Evolution. It is thought that the investigations recorded in the following pages, in revealing a certain unusual condition of the chromosome complex in an insect, Hemideina thoracica White, as shown by the male germ cells may have some bearing on the problem referred to above.