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Wm. S. Marshall, 



of varying sizes. These are tlie lighter nuclei we mentioned in the 

 last stage, but which are, in this older ovary, mueh more abundant. 

 Most of them are smaller than the other nuclei but some are of an 

 equal size. Besides the Variation in size, they show a considerable 

 amount of difference in the number and size of the contained chromatin 

 granules. These are the nuclei of the primitive nurse-cells just after 

 division ; they increase in size and in the amount of chromatin granules 

 as they grow and prepare to divide again. 



Dividing nuclei are found in any part of this ovary but are more 

 abundant in its middle portion. They are not more numerous here 

 than in the last stage. In the equatorial-plate stage a rather indistinct 

 centrosome is often seen from which radiate a few fibres, but these 

 are short and not abundant (Fig. 33). The same is true of a later 

 stage (Fig. 34). After completion of division (Fig. 35) a few small 

 mid-bodies are seen at the boundaries of the new cells. The nuclei 

 of the daughter-cells are small, and their contents indistinct, but we 

 can distinguish a reticulum and a few chromatin granules in each. 



Along the margin of the tubule, in this middle part, are a few 

 nuclei (Fig. 36) similar in structure to those in the long distal portion. 

 These are the nuclei of the future epithelial cells; they do not here, 

 as in the distal region, all lie with their long axis across the tubule. 



Ovary F. As pupal development goes on, we find the ovary 

 increasing in length, and the differentiation of the nuclei becoming 

 more marked. The next we take, ovary F, is from a pupa the 

 ovarian tubules of which are each 2,1 mm in length. The long 

 distal portion remains the same as we have found in younger stages, 

 but in the middle region, a considerable change has taken place, 

 and we now, for the first time, find that the older oöcyte nuclei are 

 entirely different from those of the nurse-cells. 



A study of the difi'erent nuclei shows us that, proximally in the 

 distal portion (Fig. 37, position 38), they are generally of an oval 

 form (Fig. 38) but larger than corresponding nuclei of the younger 

 stages. In this, and many neighboring cells, we find a round body 

 which does not stain, but is darker and denser than the surrounding 

 cytoplasm; it generally, as here (Fig. 38), occupies a position between 

 the nucleus and the free end of the cell, but may also be on the 

 opposite side. 



Where the distal passes over into the middle portion of the 

 tubule (Fig. 37 x — x) we find, as described in earlier stages, that a 



