212 Mr J. M. Macfarlanc on the 



nuclei are connected only by a narrow band, a small 

 spherical part in the centre of the septum beiug yet in 

 process of formation (Plate X. fig. 14). Finally, when 

 the septum is completed, the two perfectly-formed sister 

 nuclei — each suspended in its own cell— may indicate 

 their relationship by a connecting protoplasmic strand 

 exactly like those which moor the nucleus in its place 

 (Plate X. fig. 15). 



An interesting question is here opened up. Whence 

 are these threads or strands derived, and what is their 

 functional value ? From the examination of a large num- 

 ber of my preparations, I can scarcely resist the conclusion 

 that they are fibres of the nuclear barrel, and therefore — 

 to trace back their parentage further — fibres of the intra- 

 nuclear network, which, as the barrel wanes, are detached 

 from it, and in some way or other become united to the 

 chlorophyll bands. Certain it is that new ones do originate, 

 and it is possible that they may be formed by splitting or 

 bifurcation of the older ones, this being continued to the 

 base of attachment of the filament. At the same time it 

 is equally probable that their origin is to be traced in the 

 manner previously indicated. Would these threads then 

 constitute the intracellular network of Klein ? In work- 

 ing at vegetable cell- structure I confess that the idea of a 

 distinct series of fibres permeating the cell has appeared 

 to me scarcely tenable, the apparent network in many cases 

 resulting from mere vacuolation of the protoplasm. In 

 Spirogyra, however, one cannot quite get rid of the fact 

 that these threads do not result thus, and that they play so 

 important a part in the life history of the cell; in truth, it 

 seems that here an intracellular network exists. Some 

 rather novel views have recently been prg^pounded as to the 

 function of this network in animal cells. In Spirogyra I 

 can only say that these seem to be (a) to moor the nucleus 

 in the centre of the cell ; (h) to supply it with nutrient 

 matter when in the ordinary resting state ; and (c) to 

 convey a plentiful supply when division is going on, 



I would now revert to the formation of the cell-septum 

 by the protoplasm, and the attaching or j^lastering of this 

 to the cell-wall. In Spirogyra it has generally been 

 accepted that the septum arises as a process inwards from 



