52 THOS. H. MONTGOMERY jr., 



Duclear membrane is still present, a fact which is of value in deter- 

 mining their mode of origin in Pentatoma. But another possibility 

 in regard to their mode of origin remains to be mentioned: it might 

 be assumed that they are formed from the nucleolar masses which 

 lie opposite the centrosomes. I have noticed such masses which 

 appeared to be transversed by mantle fibres, but this observation does 

 not prove anything. The nucleolar masses disappear at the time that 

 the nuclear membrane does , but this is generally characteristic of 

 nucleoli in mitosis. Strasburger ('97) is nearly the only author who 

 ascribes a nucleolar origin to spindle fibres. 



The idiozome in the early prophases (Id.Z, Figs. 101, 102, 105) 

 has the same position as in the rest stage, but subsequently decreases 

 in amount (Figs. 119—121, 137, 138), and at the time when the pole 

 rays are well developed remnants of it are to be seen at the periphery 

 of the equator of the spindle (Figs. 153 — 158). Only in a very few 

 cases are any traces of it to be seen near the centrosomes (Fig. 158). 

 If we regard the pole rays as fibres which exert a pushing force, for 

 which my observations on Pentatoma ofi'er some support, they might 

 be considered the mechanical agents in the movement of the idiozome 

 granules towards the equator of the spindle. In cells of the larger 

 generation a greater amount of this substance remains in mitosis, 

 corresponding to its greater volume in the resting cell. There is no 

 reason for supposing that it becomes changed into the astral rays, 

 on account of the persistence of some of it during mitosis; but what 

 becomes of that which disappears could not be determined. 



"With the disappearance of the nuclear membrane we find the 

 large, clear nuclear cavity, in which the 7 chromosomes lie irregularly 

 arranged, and which is bounded by the pole fibres (Figs. 160 — 165). 

 In fact all the cytoplasm seems to become arranged in the polar 

 radiation, except in cells of large diameter, where a reticular cyto- 

 plasmic appearance persists at the periphery of the equator, seldom 

 at the poles of the cell (Figs. 167, 173); this of course would 

 correspond to the terminal reticulation of astral rays in other objects. 

 To each end of each chromosome are attached two mantle fibres 

 (Figs. 160 — 169, 172 — 175); thus the same number of mantle fibres 

 to each chromosome as in the spermatogonic mitoses. These are 

 thicker than the pole rays. Before the nuclear membrane disappeared, 

 it was impossible to determine exactly how many fibres were attached 

 to each chromosome, though in some cases it appeared that as may 

 as 3 or 4 were appHed to each end of some of the latter (Fig. 156); 



