214 Mr J. M. Macfarlane on the 



nucleus has gained in importance, in like ratio, we might 

 say, has the nucleolus declined. Some patent reasons can 

 be given for this course. I have already asserted of 

 OrnitJiogalum and SciUa that the nucleus is the last of the 

 three factors to divide, and — though at first sight it might 

 not strike one — the same is true of Spirogyra ; further, 

 that an influence radiates from the centre outwards, and 

 this influence is placed in the nucleolus. It may be that 

 the nucleolo-nucleus has a phylogenetic rather than a func- 

 tional interest ; but, granting this, the nucleolus remains. 

 We have seen that previous to its fission the nucleoplasm 

 was repelled on each side ; that on these sides the nuclear 

 membrane first dissolved ; that on division the nucleoplasm 

 still further retreated ; that as the daughter nucleoli moved 

 apart a radiant repelling influence originated the broad 

 nuclear barrel ; and that only after these had buried them- 

 selves in the polar masses of nucleoplasm did the latter 

 close up and subsequently form an encircling membrane. 

 It may be said that agents simultaneous with, hut separate 

 from those in the nucleolus were at work in the protoplasm 

 forming the granular aggregations first noticed by Stras- 

 burger, but not a trace of these is observable when the 

 changes shown in Plate X. figs 3a and 36, are progressing; 

 as well, therefore, may an impulse travel out setting up a 

 series of movements in the protoplasm, as does the aggre- 

 gation along the threads towards the nucleus indicate a 

 similar impulse in the opposite direction, propagated, in all 

 probability, originally from the centre. 



Though the nucleolus is a smaller body than the nucleus, 

 we must not on that account throw it aside. Nothing, in 

 truth, has struck me more than the firm solid consistence 

 it has when stained, compared with the latter, and quite 

 different from the staining of the intranuclear network. 

 Still more in Spirogyra the nucleolus is not insignificant, 

 as it occupies from one-fourth to one-sixth of the area of 

 the nucleus. We can, therefore, no longer regard it as a 

 trifling factor in the life of the vegetable cell, and I hope 

 soon to point out that the same holds true of the animal 

 cell. 



It must have been observed that in the foregoing descrip- 

 tions of cell-division no phase corresponding to Strasburger's 



