12 J. BRONTE GATENBY 



Occasionally, as in PL 3, fig. 22, the nucleolus may be seen 

 to be clift'erontiated at its periphery into a number of small 

 stainable bodies which may represent the beginnings of the 

 parts to be extruded. 



In PI. 3, fig. 23, is a cell showing the appearance of the 

 nucleolar extrusions after staining in iron haematoxylin or 

 Chanipy-Kull, while in fig. 21 is a cell treated by Mann-Kopsch 

 and the nucleolar extrusions ai)pear as pale yellowish bodies. 



From the stages represented by PI. 3, figs. 21 or 23 onwards, 

 there is generally marked difficulty in ascertaining the exact 

 fate of the nucleolar extrusions. This is due to the fact that 

 just about this period a second process is set into motion ; 

 this consists of an appearance all around the nuclear membrane 

 of a chromophil cloud, which in most preparations obscures 

 the nucleolar extrusions ; an exaggerated example of this is 

 drawn in PI. 4, fig. 35, from a silver nitrate Da Fano prepara- 

 tion, but the cloud does not show so darkly with Benda or 

 iron alum haematoxylin. 



At all events there begins at this period a peri-nuclear 

 activity, which also corresponds with the change of the chromo- 

 phility of the egg cytoplasm from a primary oxyphilia to 

 a basophilia. Two other occurrences also tend to obscure the 

 peri-nuclear nucleolar bodies at this period : around each body 

 a clearly-defined vacuole often appears (PI. 4, fig. 29, nlv, 

 from a Mann-Kopsch preparation), and moreover the mito- 

 chondria near the nuclear membrane are now forming actively- 

 growing and dividing clusters. With iron alum haematoxylin 

 it is not possible to make sure as to the fate of the nucleolar 

 extrusions, because these and the mitochondria stain in the 

 same colour. With the Champy-Kull fixation and Benda stain 

 I have found examples which, I believe, establish as a fact my 

 view that the nucleolar extrusions first lose their connexion 

 with the nuclear membrane and then either pass right away 

 into the cytoplasm or immediately begin to break up into 

 much smaller fragments. As with the mode of appearance 

 itself of the nucleolar extrusions, so also the subsequent 

 behaviour of these bodies is open to a good deal of variation. 



