1 22 Transactions of the Society. 



have the appearance of specialized ends. Another remarkable 

 feature is that in suitable cases (see figs. I) and l'») it will be readily 

 seen that the spindle fibres of each bundle, as they near the apex 

 of each chromosome, converge, not to a single extremity, as lias 

 hitherto been depicted and described, but to a double end, one for 

 each " chromatin extension " with which they are in apparent 

 contact, though they do not, I believe, actually fuse. 



In conclusion, it seems important from the foregoing to realize 

 that due consideration should be given to the three following 

 points of great interest : — 



1. The chromatin extensions to be seen at the V-shaped 

 extremity of each chromosome. 



2. The double end of each bundle of spindle fibres, one directed 

 to each chromatin extension. 



3. The extra staining capacity of the ends of these spindle 

 fibres. 



It would seem, perhaps, inadvisable to draw too hasty a con- 

 clusion as to which of these three very important details demands 

 most attention, when considering what bearing they have upon or 

 what their relation may be to the mechanism of mitosis. 



I do not wish to pose for one moment as a physicist in the strict 

 sense of the word, but I do feel inclined to ascribe the greatest 

 weight and importance to No. 3 of the above items. 



Relying not unduly upon the results of many of our present- 

 day staining reactions, it may with safety be asserted that if a 

 portion of a structure or tissue can be acted upon by a stain or 

 staining process with a greater intensity, and also offer a greater 

 resistance to differentiation or extraction of this stain, after the 

 application of suitable means for this purpose, than the surrounding 

 tissues, one may assume with some degree of certainty that the 

 tissue so reacting possesses some special (may I say vital or 

 organic ?) functional capacity. 



That the portion of the spindle fibres above mentioned does 

 react in the specialized manner just referred to the methods given 

 is, I think, conclusively demonstrated ; and it but remains for us to 

 attempt to work out the important question, " What force, vitality, 

 or biochemical action can be hidden in so concentrated and 

 minute a portion of the spindle fibre structure seen in mitosis ? " 



That the items Xo. 1 and 2 also possess undoubted significance 

 must also be accepted, and each must latter receive its full mead of 

 consideration. 



