216 Mr J. M. Macfarlane 07i the 



polos together are his nuclear disc. This latter is a pale area 

 traversed by delicate threads meeting at the opposite ends. 

 The central band then breaks up, and flows irregularly 

 towards the two poles (Plate IX. fig. 22) along the pale 

 threads, and there aggregates to form the masses of the two 

 daughter nuclei (Plate IX. fig. 23). These have the same 

 shining surface which the nuclear plate had, and only in 

 some cases have I managed by staining to reveal nucleoli in 

 the interior. Connecting the daughter nuclei is a fibrous 

 bridge, the nuclear barrel, and there early appears in this one 

 or two rows of granules, the cell-plate (Plate IX. fig. 24). 

 The nuclear barrel, from being about one-third the width of 

 the cell, is expanded till it completely spans the latter, or 

 nearly so (Plate IX. figs. 25-29), the cell-plate keeping pace 

 with it. Along the cell-plate the new septum is laid down, 

 after which the halves of the nuclear barrel fuse with the 

 surrounding protoplasm, and two sister nuclei in sister cells 

 now bring the cycle of change to a close. 



Though on first formation of the daughter nuclei they are 

 pellucid and difficult to resolve, as increase of the nuclear 

 barrel goes on this passes off; and then it is seen that fre- 

 quently two nucleoli are in each nucleus (Plate IX. figs. 

 25-29). In the hypodermal cells only the steps from forma- 

 tion of daughter nuclei onwards are traceable ; these cells 

 therefore correspond to those of Spirogyra, Ornithogalum, 

 and Sciilla, in having no nuclear plate phase. How then is 

 this difference in the two kinds of cell to be accounted for ? 

 As yet I do not venture to reply, since my study of the plant 

 is not completed. 



Looking now at the four plants passed under review, the 

 general results as to division, applicable in all, may be 

 summed up as follows : — 



(a) In division of the cell the nucleolo-nucleus probably 

 divides first. 



(6) The nucleolus undoubtedly divides next, and this is 

 followed by division of the nucleus. 



(c) During division of the nucleus a nuclear plate with 

 nuclear disc is formed occasionally. 



(d) If a septum is laid down, tliis is always preceded by 

 formation of a nuclear barrel and cell-plate. 



The general facts which have been advanced as to cell- 



