L20 Transactions of the Society. 



paper, ami may appear to many insufficiently trustworthy and 

 simple to follow, I would emphasize the statement that it only 

 requires a worker to make a start in order to convince himself 

 that this is certainly not always the case. Here we certainly have 

 an important method and subject, and I feel sure that anyone who 

 will follow them up will be amply rewarded. 



In giving the description of the newly disclosed structure to 

 which I have already referred, I find it difficult to decide on a 

 name or term to assign to it. 



Up to the present, for want of a more applicable or appropriate 

 term, I have made use of the word "structure," but now, for the 

 purpose of this paper, I shall use the term " chromatin extensions." 



In order to fully understand these chromatic extensions and 

 appreciate their possible value, and the part they may play in pro- 

 ducing and controlling certain of the movements of the chromosomes, 

 it is important that we should make ourselves familiar with the 

 relation which the chromosomes and spindle fibres bear to each 

 other, the theories concerning these structures which have at 

 different times been put forward, and their various actions described 

 at length, and the now accepted part played in the process of 

 mitosis by the spindle fibres. 



In connexion with these points, I would recommend those 

 sufficiently interested in the subject to make a careful study of the 

 plates given in Strasburger's "Practical Botany," translated by 

 W. Hillhouse, M.A., etc., 1908 edition, pp. 442, 461, 463. 



Although a little diagrammatic in one or two instances, they 

 enable one to obtain a clear idea of the correct relations and 

 position of the chromosomes and spindle fibres at metakinesis as 

 well as graduating earlier and later stages. 



It is generally believed by cytologists, and I think rightly so, 

 that during metakinesis, as well as a little before and after the 

 metakinetic stage, the chromosomes stain at their best, i.e. most 

 intensely. Hence, when this is reinforced by my special method 

 (as given above) of treating vegetable sections, not only the 

 chromatin material is brought into a still further improved con- 

 dition to receive stain (apart from its own specificity in this respect), 

 but also — and here I claim a good advance upon former technique 

 — the archoplasmic structure spindle fibres are also brought into a 

 more favourable condition for taking up the stain. 



As is well known, it is most difficult to get such structures to 

 react with any kind of stain, and when they do, the amount of 

 stain absorbed is so slight that it is scarcely appreciable. 



It is recognized also that there may be two modes by which 

 the chromosomes split or divide into two quite equal parts. I 

 allude here to the splitting which takes place immediately following 

 the definite arrangement of the chromosomes forming the equatorial 

 cell plate (metakinesis), resulting after their reassembling at the 



