GOO Transactions of the Society. 



mosomes. Sometimes when the depth of stain is not too dense to 

 make out any detail, it will be observed that that part lying close 

 to the chromatin shows a slightly deeper shade than that farther 

 towards the centre. The exact manner in which the nucleolus is 

 injected is at present rather uncertain for me to state definitely; 

 and perhaps for a while too much weight should not be put upon 

 the following remarks until more work and observation have been 

 carried out. 



At or about the time when the line of division of the cell into 

 two is well marked, and what remains of the interzonal fibres has 

 nearly always disappeared, and in some instances when the 

 daughter nuclei have made an attempt at regaining a spherical or 

 oval shape, the nucleoli make their appearance in the loops. 



It is difficult to say whether this occurs gradually by streaming 

 in, or takes place with a sudden inrush, bursting, or pouring. 

 Personally I give preference to the former mode, and in support of 

 this view a careful observation of fig. D should be made. Here 

 it will be seen that the upper nucleolus is well developed and 

 occupies a good portion of the area of the loop, whilst the lower, 

 from the centre downwards, is wasted off until at its lowest ex- 

 tremity, which is somewhat broadened, appears fused to the chro- 

 matin. At the completion of the formation of the nucleolus nothing 

 is left but one, occasionally two or more, very fine drawn-out 

 processes marking its attachment or association to the chromatin. 

 These exist for varying lengths of time, and eventually disappear 

 entirely. During the time they are to be seen they should not 

 be taken for linin thread — a mistake which can very easily happen. 



For a fuller account of these processes a reference should be 

 made to my previous paper and photographic reproductions. 



When the nucleolus has made itself manifest, it is in many 

 instances of a size somewhat proportionate to that of its loop, and 

 again it may be very small. 



In the latter case the nucleolus is more often than not very 

 close to or apparently in contact with the chromatin. 



The position in the loop at which it may appear is not constant, 

 and may vary in such a manner that I am inclined to think the 

 shape of the loop may have some influence in this respect. 



This latter remark is at present only an assumption on my 

 part, and may be purely imaginary. 



However, if the loops be round, or nearly so, the nucleolus may 

 start to form at any position. On the other hand, if their outline 

 be at all irregular or distorted, it appears to choose for its 

 developing point one of the irregular situations. 



This brings me to the part of my subject in which I wish to 

 put before your notice my views as to what I believe to be the 

 actual manner in which the nucleolus makes its re-appearance or 

 disappearance. 



