BLACKMAN: SPERMATOGENESIS OF THE MYRIAPODS. 69 



seuted in figs. 25 to 30. In fig. 26 the itomere has nearly constricted 

 ofP from the nucleus. In fig. 27 it has left the nucleus and is seen 

 free in the cytoplasm, surrounded by a rather well-defined membrane. 

 The nuclear membrane remains open at the point from which it was 

 constricted, and the course the itomere has taken through the cyto- 

 plasm is plainly visible. In fig. 28 it is seen extending from the 

 nucleus, with which it is still connected, to the cell membrane. In 

 fig. 28 it has reached the cell membrane, and in fig. 29 has been ex- 

 truded and the membrane has apparently closed behind it. 



In all these cases the nucleus has remained open, and the pathway 

 left by the itomere in its passage through the cytoplasm can be 

 plainly distinguished. The best stain for demonstrating the stages 

 just described is obtained by using Heidenhain's iron-hsematoxylin 

 in connection with Congo red. The chromatin, as usual, takes on a 

 dense black stain, that of the nucleus and that of the itomere stain- 

 ing precisely alike. The ground substance of the cytoplasm takes on 

 a transparent red stain, against which the fibers forming the reticu- 

 lum stand out plainly. The pathway left by the itomere stains a 

 little darker red than the groundwork of the reticulum. 



The budding process and the extrusion of the itomere is accom- 

 panied and succeeded by a great increase in the size of the cell, as 

 can plainly be seen by consulting the plates. At first this growth is 

 more marked in the cytoplasm (figs. 21-27), but later the nucleus 

 also grows, although not in proportion to the cytoplasm. (Figs. 29- 

 31.) As far as I am informed, such a remarkable increase in the 

 amount of cytoplasm has never been described in the spermatids. 



During this growth period masses of deutoplasm are present in the 

 cells in more or less abundance. The first evidence of yolk observed 

 in the spermatids appears at the time of the protrusion of the itomere. 



Thus the formation and extrusion of the itomere seem to have 

 some connection with the succeeding growth of the cell and the ap- 

 pearance of yolk substance, as well as with the origin of another struc- 

 ture concerning which I shall speak later. 



I wish now to return to a consideration of the behavior of thecentro- 

 some. The last time the centrosome was mentioned it was a rather 

 small, darkly staining body, in close contact with the cell membrane, 

 upon that side of the cell farthest from the plane of division. At this 

 time no radiations are to be seen proceeding from it and it is sur- 

 rounded by no idiozome or attraction sphere. From this place the cen- 

 trosome can be traced for a time, but is lost. Later it reappears, and 

 from this time can be traced to its final position in the middle piece 

 of the spermatozotm. It leaves its place upon the membrane and, up 

 to a time when the budding process is well under way, may be seen at 

 various places in the cytoplasm. There it disappears and is not again 



