Disappearance of Nucleolus in Mitosis. By E. J. Sheppard, 553 



apparent, so much so that the nucleolus at this particular period 

 presents a character similar to a capillary plexus (plate XIX. fig. 1). 

 The staining, although much less pronounced, still remains more 

 marked at the circumference. 



It will be also noticed in the quiescent state that the majority 

 of nucleoli are spherical ; a few here and there may be observed in 

 a more or less oval form, according perhaps as they may or may 

 not be affected by the shape of the nuclei. 



Again, at or nearing the completion of the spireme the nucleoli 

 contract considerably, their outline becoming very irregular and 

 much distorted, and in places having projecting processes not 

 unlike small pseudopodia. 



If very careful and critical observation under high power be 

 conducted on cells in this particular phase, it will be observed in 

 some that a very fine thread-like process, similar to that found 

 connecting the several nuclei in the polymorphonuclear leucocytes 

 in human blood, extends from the ends of these pseudopodia just 

 mentioned, and is connected with the chromatin thread (plate XIX. 

 figs. 2, 3). Much care is required in sighting these very fine 

 structures, as their staining power not being very great they may be 

 easily overlooked in consequence of the surrounding masses of other 

 structure. 



It may be not at all unlikely that by these processes just 

 described the nucleoli are drawn into the nuclear thread, but the 

 somewhat comparatively few cells to be found possessing these 

 fine processes may leave a doubt in this direction. 



However, the nucleoli appear at this time distinctly more 

 granular in character, and so intimately associated with the 

 nuclear thread, that finally its absolute disappearance takes place 

 in such a manner that one is led to believe that it is taken up or 

 entirely absorbed by the latter. 



In the three figures (plate XIX. figs. 4, 5, 6), where a very late 

 disappearance is exhibited, it will be observed that in fig. -i the 

 nucleolus is in contact with the crown, in fig. 5 near the end, and 

 in fig. 6 absolutely at the end of a chromosome. 



Much controversy and many theories have been advanced 

 regarding the disappearance of the nucleolus in mitosis. Certainly 

 it is a subject that requires a great amount of careful study, minute 

 observations and investigations to be made before being in a 

 position to come to any definite conclusion ; but many of the 

 preparations I have made, and the study of them from time to time, 

 especially those of the epidermis of tadpole, and growing roots 

 of Hyacinthus, have induced me to bring before your consideration 

 this interesting subject. 



In conclusion I should like to say that of all the methods, 

 staining, and others tried by me, none have given such even 

 results as the above. The observations, etc., mentioned are the 



