204 Page May and Walker 



The nucleolus here dealt with is generall}- spherical in shape, occasionally 

 oval. It is bounded by a definite membrane, and the contents are usually 

 homogeneous or finely granular in structure. As compared with the 

 chromatin present with it in the nucleus, its staining reaction is acid. 

 Small aggregations of chromatin are almost invariably found lying upon 

 the outer surface of the membrane of the nucleolus. These small collections 

 of chromatin are often continuous with the chromatin granules in the linin 

 of the nucleus, and are so closely applied to the outer surface of the membrane 

 tliat it is only in specimens specially stained for the purpose that their 

 actual position can be ascertained. Without this examination it is also 

 difficult to be sure as to the staining reaction of the nucleolar material 

 proper, as this is masked by the chromatin lying upon the surface.^ 



Several nucleoli are frequently found in the nuclei of nerve cells, indeed 

 the present observations indicate that more than one is usual. Frequently 

 there are four or five, or more,^ which may vary greatly in size. 



In many cases a small excrescence may be seen at one point at the 

 margin of the nucleolus, and perhaps this is more usual w^here only one 

 large nucleolus is present (tigs. 1 and 2). Generally, if not always, one or 

 more of the chromatin aggregates already mentioned as being observed 

 upon the nucleolar membrane are found to be present upon the outer 

 surface of these excrescences, in sections specially stained for the purpose 

 (figs. 1 and 2). Other cells are found where the excrescence has apparentl}^ 

 increased in size and travelled away from the nucleolus, being still attached 

 to it by a process of the membrane. This process seems to persist until 

 what was originally the excrescence has grown to a considerable size (figs. 

 3 to 5). Cells are also frequently to be found which exhibit traces of 

 what was evidently the connection between the nucleolus and the excres- 

 cence, and where the excrescence has attained a size which approaches or 

 equals that of the nucleolus (figs. 6 and 7). A careful examination of the 

 appearance of the nucleolus and of the excrescence up to the time when, 

 according to the present interpretation, they are separated from each other, 

 shows that both are exactly similar in structure, and that there may be 

 several similar nucleoli undergoing similar processes in the same nucleus. 

 It is, in fact, easy to find, in the same slide, every stage between the single 

 nucleolus with one or more small excrescences, and two distinct nucleoli, 

 which are almost exactly similar to each other. From this it is equally 

 easy to pass on to cells with four and five nucleoli, or even more (fig. 8). 

 The structure of these bodies is so definite that there is no possibility of 

 mistaking them, in a properly preserved specimen, for any other nuclear 

 constituent, such as a mass of chromatin. 



Very rarely a nucleolus may be seen dividing by a process analogous 

 to amitosis, or to the division of a drop of viscous fluid into two (fig. 9).^ 



The many observations with regard to the migration of the nucleoli 



^ Method C. - We have counted as many as nine in one nucleus. 



^ "We have onlv observed this twice in inanv hundreds of cells. 



