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Wm. S. Marshall, 



we find a nearly similar structure. There are here however two 

 nucleoli instead of one and, as in older stages, we always find them 

 more in number, we judge that here this increase has begun. Here 

 also we find tbe nucleoli always staining and they become the most 

 prominent structures within the nurse-cell nncleus. 



In OYary C, we have for the first time fonnd that oöcytes and 

 nurse-cells have become dilBferentiated and many of them arranged 

 in groups, each one of which will, in still later stages, form a 

 Chamber. In the youngest group we can here distinguish as such, 

 we find that the only difference between oöcyte and nurse-cell, 

 is in the larger size of the former; their nuclei are, both as to size 

 and structure, alike. The paired chromosomes which both contain, 

 are at first similar, but here in this larval stage, ovary C, those 

 within the nurse-cell nuclei begin to change and from them come 

 a large number of small chromatin granules. The Single achromatin 

 nucleolus of the nurse-cell nuclei persists throughout, but at a little 

 later stage, ovary D, we always find more than one. While the 

 nurse-cell nucleus has passed through these changes that of the 

 oöcyte remains unchanged. 



Ovary D. This larval ovary shows (Fig. 34) that it is somewhat 

 older than the last; there are as yet no Chambers formed but the 

 three oldest groups of oöcyte and nurse-cells are arranged in the 

 Center of the tubule. In the last ovary we described the proximal 

 half of the tubule, and, as in this one nothing diflferent in cellular 

 structure is shown, we shall confine the description to what is found 

 in the distal part. 



Here (Fig. 35) we find a more distinct epithelial layer than is 

 generally seen. The cells composing it are in difi'erent stages of 

 development: uudififerentiated nuclei, a\ some with large chromatiu 

 granules, h\ and those in which the threads have begun to be 

 formed, c. Of these the undifferentiated kind, a, are found along 

 the margin and most of them close to the distal end of the tubule; 

 the other two kinds are found both at, and away from, the margin. 

 In the Center different stages in the formation of the spireme-thread 

 are seen and some nuclei in synapsis. The most proximal of all 

 the nuclei are seen to have the paired chromosomes already formed. 

 All of these nuclei have an achromatin nucleus. 



Ovary E. This tubule (Fig. 7) is from the ovary of a pupa; it 

 has five well developed Chambers each with an oöcyte and the ac- 



