Contr. towards the Embryology and Anatomy of Polystes pallipes. 191 



the same relative place that tliey were in the last stage, namely, at 

 the distal end of the median portion of the tubule. At this region 

 cells occur abundantly in the middle of the tubule and a majority 

 have larger and more spherical nuclei. Near this region, we find 

 the first cells which we can surely determine as oöcyte or as primitive 

 nurse-cells, although as yet the difiference is not very marked. Both 

 of these cells, or their nuclei (Fig. 28 a and are still quite similar 

 to those we find throughout the terminal portion of the tubule, and 

 are therefore not very distinctly separated from each other. Further 

 down the tubule the differentiation becomes more marked; we find 

 the nuclei of the primitive nurse-cells spherical, and with a round 

 darkly staining chromatin body, while the oöcyte nucleus is larger, 

 and of an irregulär form, containing one or two rather large nucleoli 

 and a few small, but distinct, chromatin bodies (Fig. 29 a and h). 

 The latter nucleus appears lighter than the former, due to the smaller 

 amount of matter in it, and most of this is on the periphery. Others 

 have noticed the lighter appearance of the oöcyte nucleus even 

 as long ago as Claus (7). This is hard to show in the drawings, 

 but after one has studied these nuclei for some time, those of the 

 oöcytes, can generally be distinguished by their lighter and clearer 

 appearance. 



We notice here a greater Variation in the structure of the nurse- 

 cell nuclei and find that, in general, there is some relation between 

 these and their position in the tubule. Somewhat further down 

 (Fig. 26 place 30), we find that the chromatin granules in many of 

 the nuclei have become larger and that each is imbedded in a small, 

 irregulär mass of achromatin. Such nuclei may be found almost any 

 place within the proximal three-quarters of the middle section of the 

 tubule, but they are not found near its distal end. In the same 

 region, but not quite so far distal, are a few nuclei which show a 

 number of chromosomes; a stage undoubtedly preparatory to the 

 division of the primitive nurse-cells. If such a stage is found before 

 each division we cannot say, as it has been impossible to distinguish 

 the dififerent divisions from each other. The chromosomes are curved, 

 beaded rods; besides these the nucleus contains a fine fibrillar 

 achromatin substance, but, whether it connects the chromosomes to 

 each other, we could not determine. In the proximal half of the 

 middle portion of the tubule are a number of lighter nuclei, not large 

 and irregulär as are those of the oöcytes, but small and spherical, 

 with an indistinct reticulum, in which lie a few chromatin granules 



13* 



