On the morphology of the chromosome group in Brachystola magna

Abstract

The appearance of Boveri's recent remarkable paper' on the analysis of the nucleus by means of observations on double-fertilized eggs has prompted me to make a preliminary communication of certain results obtained in a general study of the germ-cells of the great lubber grasshopper, Brachystola magna. As will appear from a glance at the figures given in my former paper2 upon the same form, the cells of Brachystola, like those of many amphibia, selachians and insects and certain of the flowering plants, exhibit a chromosome group, the members of which show distinct differences in size. Accordingly, one feature of this later study has been a critical examination of large numbers of dividing cells (mainly from the testis) in order to determine whether, as has usually been taken for granted, these differences are merely a matter of chance, or whether, in accordance with the view recently expressed by Montgomery,3 in regard to a certain pair of elements in the nuclei of one of the Hemiptera, characteristic size-relations are a constant attribute of the chromosomes individually considered. With the aid of camera drawings of the chromosome group in the various cell-generations, I will give below a brief account of the evidence which has led me to adopt the latter conclusion. In the first generation of secondary spermatogonia, which are the earliest germ-cells I have been able to obtain in Brachystola, certain differences in length and volume are to be seen between the members of the chromosome group. These cells, as shown in my former paper already referred to (where they are errone-