62 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



The stage represented in Figure 79 may be taken as the starting-point 

 in the transformation of the spermatid into the spermatozoon. The 

 first changes which occur are unusual and rather remarkable. We have 

 already noticed that the nucleus, since its formation in the telophase 

 of the second spermatocyte mitosis, has increased considerably in size. 

 The membrane in all these early stages (Figs. 78, 79) is unmistakably 

 present and quite evident. Now, however, before the usual transforma- 

 tion processes begin, the volume of the nucleus increases very rapidly 

 until it is more than twice as great as in the stage just described (com- 

 pare Fig. 79 with Figs. 84, 85). This is accomplished by the imbibition 

 of material from the cytoplasm by the nucleus. The taking up of material 

 is probably not accomplished exclusively by an osmotic interchange 

 through the nuclear membrane, but is so rapid that the membrane 

 seems invariably to be ruptured. Appearances similar to Figure 80 

 are extremely numerous in my material at this stage, and there can be 

 no doubt that they represent a regular process which occurs in the sper- 

 matid just before the migration of the centrosome from the cell mem- 

 brane toward the nucleus. 



The more usual appearance is shown in Figure 80. Here the nuclear 

 membrane has ruptured at two places, and the cytoplasm in the vicinity 

 of these ruptures has lost its affinity for the Congo red, the cytoplasmic 

 stain used in this preparation, and remains unstained, which is character- 

 istic of karyolymph. This presents the appearance of a rupture of the 

 nucleus by pressure from within and the extrusion of a part of its liquid 

 contents ; but that such is not normally the case, is shown conclusively 

 by a study of the stages immediately preceding and succeeding the one 

 in question. That there must be a very considerable imbibition of cyto- 

 plasmic material is shown by the great increase in size and the rapidity 

 with which it is accomplished, as well as by the morphological appear- 

 ances described. It is also very probable, as we shall see later, that 

 other activities of the cell are influenced by this phenomenon. 



In my first paper on Scolopendra I described a process of nuclear 

 budding by which a portion of the nucleus containing one or more 

 bodies of chromatin was constricted off, and migrated out through the 

 cytoplasm. At that time I considered the budding a normal process. 

 Now, after much more extensive study, I have changed my opinion and 

 do not believe this is a normal condition, for while such fragmentation 

 of the nuclear material is occasionally met with, it is not common. 

 Doubtless it is an accidental modification of the process I have already 

 described. It is probable that, owing to the rapid taking in of fluid 



