Contr. toward3 tlie Embryology and Anatomy of Polistes pallipes. 203 



cells have nearly surrounded the oöcyte but the structure of their 

 nuclei also remaius unchanged (Fig. 81). In the nurse cliamber, or 

 what will later be such, a number of epithelial cells are seen aloüg 

 the margin. Whether or not they form a complete layer here is 

 doubtful. In Our drawing (Fig. 80) one sees such a layer, but it 

 would be hard to duplicate this regularity in many of the sections. 

 These marginal epithelial cells, as well as those scattered in among 

 the nurse- cells, have nuclei similar in structure (Fig. 82) to those 

 around the oöcyte. 



In the later stages we will not as heretofore study different 

 ovarian tubules but will give separately the history of each kind 

 of cell. 



The epithelial cells have been found present in both kinds of 

 Chambers; of those in the nurse Chamber there is nothing further to 

 say, they remain for a long time unchanged but finally stain much 

 lighter. Part of them are left within the old Chamber after all the 

 nurse-cells have disappeared, and others very likely go as nourish- 

 ment to the developing oöcyte. Those epithelial cells which form 

 a follicle around the oöcyte have a further history but this can be 

 better given if, as is hoped, we at some future time can take up 

 the formation of the chorion. 



For a considerable time as development goes ou, the nurse-cells 

 show no further change, remaining as we have described them 

 (Fig. 63). They have already shown, in the cytoplasm around the 

 nucleus, secretory activity, and this, as they grow older, becomes 

 more apparent; later we notice, as has been described for the nurse 

 cell nuclei of so many insects, that they become irregulär in form 

 sending out pointed processes into the cell. In Polistes this is never 

 so marked as in many other insects. The darkened layer of cyto- 

 plasm around the nucleus becomes thicker and within it a number 

 of vacuoles finally appear (Fig. 85). Between egg and nurse Chamber 

 an opening exists (Figs. 84, 86 and 88), and through this the oöcyte 

 often sends a lobate process, this and the nearby cytoplasm of the 

 oöcyte, is often seen to have a dark stringy appearance which is 

 undoubtedly due to the activity of this process in the absorption of 

 nourishment. Older nurse-cell nuclei loose, to a great extent, their 

 irregulär appearance and become again more normal in shape; finally, 

 when much older (Fig. 86), the cells loose in part their outline, the 

 Chamber becomes emptier as if less cells were in it than formally. 

 All the cytoplasm is now of the same appearance as was the layer 



