132 BULLETIN OF THE 



('85, Plate I. Fig. 7) ; for the connecting thread in the dividing nucleus 

 of Aphrophora remains unstained, and therefore contains no chromatin. 



The dividing nucleus represented by Figure 8 is peculiar in several 

 respects. In the first place, the daughter nuclei are very unlike in 

 form, though this is by no means unusual with dividing nuclei from old 

 membranes. All the stainable nucleoli are in one daughter nucleus, 

 while the other still shows a faint longitudinal arrangement of its 

 chromatic threads. The sharply stained connecting thread is notched 

 at a point midway between the daughter nuclei, probably indicating 

 the place where, at a later stage, rupture would have occurred. The 

 daughter nucleus on the left is nearly destitute of chromatin in the 

 crescent-shaped space lying next the connecting thread, and an inner 

 contour line is visible {x), from the central point of which a stainable 

 cord extends to the proximal end of the connecting thread. I have seen 

 a similar appearance in the late stages of other dividing nuclei, and it 

 undoubtedly indicates the manner in which the daughter nuclei some- 

 times attain a rounded form. Occasionally, however, daughter nuclei 

 entirely separate from each other have a conical or tapered form. 



In the last stages of division, the connecting thread is drawn out to 

 extreme tenuity (Figs. 9 and 10). So exceedingly fiue does this thread 

 become, that, with the highest power accessible to me (Zeiss's homoge- 

 neous immersion objective j\), I could barely trace its course through 

 the cytoplasm, though in most cases I made out that it was continuous 

 from nucleus to nucleus. It is finally broken at or near the centre, and 

 the proximal tips, as Blochmann suggests, are probably absorbed by the 

 daughter nuclei. In even so late a stage as that shown by Figure 10, 

 the longitudinal chromatic filaments are still perceptible. The right- 

 hand daughter nucleus contains four loop-shaped bodies that strongly 

 resemble chromosomes. They are, however, almost unstained by heema- 

 toxylin. 



Blochmann states ('85, p. 482) that in no case did he find a division 

 of the cell following the division of the nucleus. As already said, the 

 great proportion of binucleate cells renders it certain that cell division 

 is not an immediate consequence of nuclear division. Although I have 

 carefully examined great numbers of binucleate cells, I have only 

 once seen a cell wall in process of formation (Fig. 27). Yet one finds 

 plenty of evidence that cell division does take place. Pairs of cells like 

 those in Figure 11 are of frequent occurrence. It is safe to infer, I 

 think, from the arrangement of the binucleate cells which surround 

 these, as well as from the correspondence in size and shape of this pair. 



