The cellular elements of the Ovary of Platyphylax designatus Walk. 229 



(Fig. 47) this cliange is sliown more clearly aud in eacli acliromatin 

 mass we still find, instead of tlie paired cliromosomes, the small 

 pieces as in the last. Loose acliromatin fibrils become, in this stage, 

 more distinct. Here will be noticed a ditference in the fate of the 

 paired chromosomes in the oöcytes and in the nurse-cells. In the 

 former we have just learned that, still remaining in the original 

 achromatin mass, they break up into a few small pieces which remain 

 in the original position. In the niirse-cell niiclei we found that this 

 reaking up occurs earlier, and the resultant pieces become scattered 

 throughout the nucleus. 



In many of the nurse-cells of these Chambers we find that the 

 nucleus shows an irregulär form; this may be a general irregularity 

 Over the entire surface (Fig. 48), or one or more deep indentations 

 at one place (Fig. 46). This has to do with the secretory activity 

 of the nurse-cells of which we will speak later. 



Concerning the epithelial cells there is little to say that cannot 

 be Seen from a view of the tubule (Fig. 41). In that part of the 

 Chamber occupied by the nurse-cells, they are almost entirely missing, 

 only a few nuclei being found along the margin. We are inclined 

 to the belief that there is here a continuous layer of epithelial cells, 

 but that the pressure from the nurse-cells has so flattened them, 

 that only here and there can they be seen. Between the Chambers 

 there are a number of long narrow cells which are much larger than 

 the others, and, excepting near its base, each is nearly empty. 

 Between each oöcyte and its accompanying nurse-cells there are also 

 a few flattened epithelial cells. All these cells have similar nuclei 

 (Fig. 50). 



We have already noticed the breaking up of the paired chromo- 

 somes of the nurse-cell nuclei into many small granules. After this 

 has occured each nucleus also contains a few irregulär bodies, 

 nucleoli, which now stain, and which we believe came from the 

 Single unstained one of the earlier stages. It has been continuously 

 present through all of the stages. Düring the further growth of the 

 nurse-cells there is no change in nuclear structure except an increase 

 in the number of nucleoli. Wether these come from the one already 

 present, or from some other substance within the nucleus, we do 

 not know. The fine achromatin fibrils are much more distinct in 

 the older stages. 



The nucleus of the oöcyte, after the breaking up of the paired 

 chromosomes, contains a large, generally vacuolated, nucleolus which 



