BLACKMAN : THE SPERMATOGENESIS OF SCOLOPENDRA. 23 



tvpe are always arranged in pairs, with their long axes parallel to the 

 longest diameter of the follicle. This is not true of the smaller type. 

 Possibly owing to some inequality of pressure, the cells of a pair in the 

 testis have apparently been forced apart or caused to rotate upon 

 each other in such a way that the bridge connecting them has been 

 destroyed and their symmetrical arrangement within the follicle has 

 been disturbed. At any rate, they no longer preserve the ideal arrange- 

 ment, but their longer axes may form any angle with that of the testis. 

 The consequence is that, while the cells of the large type are arranged 

 loosely in the testis and are surrounded by the reticular matrix which I 

 have described as existing in the intercellular spaces, those of the smaller 

 type are packed closely, so that the interspaces between the cells are 

 more nearly obliterated ; indeed, the cells of this type lose their sphe- 

 roidal form, and by pressure are converted into irregular polyhedrons. 

 Thus the mechanical conditions affecting the cells of the large type are 

 quite similar to those of the typical growing ovum, whereas the environ- 

 ment of the smaller type is more nearly that of the ordinary testicular 

 cell. The two types of cells resemble respectively the oocyte and the 

 ordinary spermatocyte. This fact, and the conditions observed in later 

 stages, allow us to affirm that cells of the smaller type differ from the 

 ordinary male sex cell much less than do those of the larger type, which 

 show in general and in many details the changes which are usually 

 considered characteristic of egg cells. 



3. Abnormal Cells. 



Besides these two well-established types, there are occasionally seen 

 in the testis abnormal variations of the cells during the vesicle stage. 

 Such a one is represented in Figure 139. These cells differ considerably 

 from the normal cells of like stage. The total amount of chromatin to 

 each cell is many times that ordinarily present in the vesicle stage. 

 This chromatin is in the form of from one to ten, or even twelve, appar- 

 ently homogeneous spherical masses connected by an extremely coarse 

 deeply staining system of chromatin bands arranged in the form of 

 a network. 



The cytoplasmic structures also present marked differences. The 

 archoplasm is apparently scanty, and is scattered in small fragments 

 here and there throughout the cytoplasm. No centrosomes are visible, 

 even after the most careful search. The cytoplasm is much coarser and 



