Cytological studies on the spimiing glands of Platypliylax etc. 403 



Figure 3 shows a cell with another interesting type of nucleus. 

 In it the nucleus occupies a very large proportion of the cell and 

 shows a peculiar, evenly convoluted appearance. Three apparent 

 anastomoses are shown (Pig. 3, a), but a careful study of the outline 

 of the nuclear membrane, on which also a careful focussing is necessary, 

 convinces us that these are, as represented in the drawing, due only 

 to the overlapping of the branches. 



Eeferring again to figure 7, we give a more detailed account, 

 taking into consideration the nuclear contents as seen from a surface 

 view. Carnoy [1] figures, from Lepidopterous larvae, three types of 

 nucleus, dependant on age; a young type, an adult type, and an old 

 type. These he shows to differ from each other not only in form, but 

 also in contents, more particularly the „nucleine". His first type, the 

 young nucleus, has a simple, unbranched structure, similar to the nuclei 

 in the small cells at the anterior end of the secretory part of the 

 gland, of Platypliylax (Fig. 1). He refrains however, from mentioning 

 the „nucleine" in this type, and he does not in his figure differenti- 

 ate it clearly. In his adult type, both branching and anastomoses are 

 present, and the „nucleine" he holds is present in the form of long, 

 slender, interwoven threads. His third, or old type shows segmen- 

 tation, both of nucleus and nuclein, the latter now forming distinct 

 pieces of irregular shapes and sizes, which are undoubtedly the same 

 structures which we shall call nucléoles. An examination of our 

 figure [7] shows the nucleus to be broken up into pieces very similar 

 to those Carnoy [1] figures as his old type. It may be seen that, at 

 first view, such a portion of nucleus might give the impression of a 

 segmented or multi-nucleate condition. A complete nucleus showing 

 such a structure as the part we represent in our figure [7] we have 

 uever seen in Platijphylax; if such occured it might easily give the 

 appearance of being segmented within any or all parts of the cell. 

 We have however, shown in this figure the typical appearance of the 

 nucléoles as found in all of our preparations, whether of large or small 

 cells, and certainly in the simpler nuclei, which - — except for lack of 

 anastomoses — conform to his second type, we find nothing giving 

 the appearance of continuous, smooth, slender threads of nuclein. The 



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