Chapter I: Introduction

Under the title, “A Peculiar Nuclear Element in the Male Reproductive Cells of Insects” (=16=), I published a preliminary account of the process characterizing the maturation divisions of the Locustidæ. This was of a general character and served merely as a basis for a description of the accessory chromosome in these cells. It is my present intention to give a detailed history of the spermatocyte divisions occurring in this family, after the manner followed previously in considering corresponding stages in the Acrididæ (=17=). Besides giving this account of processes, however, I shall be able to draw some comparisons between the two families. Eventually I hope to complete such a comparative study of all the Orthopteran families. Material for this larger investigation is now partially on hand, and is being added to as circumstances permit, so that it may be possible to carry through a study of the maturation stages in this order of insects within a few years.

The value of comparative cytological study was urged by Vom Rath (=25=), and its importance in relation to the accessory chromosome and the maturation mitoses received recognition in both my earlier papers (=16=, =17=). Recently Montgomery (=15=) has added his influence to the movement.

The observations upon which the present paper are based were originally made upon _Xiphidium_. The cells in this genus are, unfortunately, small in size, and much difficulty was experienced during the early work in getting clear images. This embarrassment was further increased by the large number of chromosomes and their habit of compact arrangement. Later it was found that species of _Anabrus_, _Orchesticus_, _Microcentra_ and _Scudderia_ have cells much better adapted for study, and because of this they have been largely utilized. The account which follows is therefore based upon a study of all these genera, and is considered representative of the family. The accompanying figures are principally from _Orchesticus_, since the number of stages represented exceeded those in material derived from other genera. I am indebted to a friend and former student, Mr. W. S. Sutton, now of Columbia University, for a generous supply of _Orchesticus_ and _Anabrus_ testes from his collections.