Re-appearance of the Nucleolus. By E. J. SJiejypard. 601 



No doubt many of you who are interested in the subject of 

 mitosis, and have read my paper upon " The Disappearance of the 

 Nucleolus," will remember the photographs that I presented to 

 your notice illustrating the fine processes extending from pro- 

 jections of the nucleolus to the chromatin. 



These become apparent soon after the loops give up their power 

 of holding the stain so deeply that nothing can be made out. 



When this period of densely staining has passed off sufficiently, 

 and the nucleolus is occupying its final position, the processes just 

 mentioned can be distinctly seen, and I am of opinion that it is by 

 these processes that the nucleolus is thrown out from or drawn 

 into the chromatin. 



Hence conies, as above mentioned, my reason fur giving 

 preference to the method by which the nucleolus may make its 

 re-appearance by a streaming-in process. 



Up to this part the above remarks apply particularly to 

 observations made upon vegetable tissues : Hi/acinthus, Allium, 

 Fritillaria, etc. 



Observations made upon animal tissues, such as frog, triton, 

 salamander, have been somewhat disappointing, and I have only 

 here been able to prove the process of re-appearance identical 

 with that of vegetable tissue up to a certain point : that of the 

 loop formations in the chromatin. These in the above-mentioned 

 Amphibia are especially well formed and beautifully distinct, as 

 reference to figs. A and C will show. 



In not a single instance up to the present — and I have 

 examined many hundreds of cells — have I been able to see a 

 nucleolus in a state of developing, or in a fully developed con- 

 dition. 



Further, I have never been able to discover in any one of these 

 loops a trace of anything resembling a nucleolus. 



What this fact points to I am unable to say ; possibly some 

 marked deviation in the process takes place here from that 

 exhibited in vegetable tissue, and remains to be worked out before 

 anything can be said upon this apparently startling difference. 



One curious point, perhaps well worthy of mention, is that I 

 have not yet succeeded in staining the included loop areas in the 

 slightest degree, this alone being a marked difference when con- 

 trasted with the results obtained in vegetable tissue. 



It might reasonably be asked what is the part played by the 

 nucleolus in mitosis. 



To such a question I would reply that in my opinion the nucle- 

 olus is an inciting or stimulating factor to the starting of the process 

 of mitosis. 



It will be frequently seen upon examining vegetable sections 

 exhibiting mitosis, that some cells have had their nucleolus wholly 

 pushed out of its socket or position in its nucleus ; and if careful 



