226 



Wm. S. Marshall, 



vacuoles. The paired chromosomes , present in the earlier stages, 

 have disappeared, but the achromatin masses, former threads, are 

 present and in each are one or more small chromatin granules, or 

 rods; there are also very many smaller achromatin bodies free from 

 these. All these parts are joined by achromatin fibrils. The outline 

 of the oöcyte nucleus is generally irregulär but not so much so as 

 are most of the nurse-cell nuclei. Within the basal part of the 

 oöcytes, are generally a number of round, dark bodies, which represent 

 some product of the metabolism of the cell; in specimens preserved 

 in Flemming, these are always black. 



In all the four oldest Chambers the nurse cell nuclei are very 

 similar. Each contains a few large, irregulär nucleoli, which stain 

 darkly, a great many small granules, also staining, and achromatin 

 fibrils connecting these. Many, but not all, of the nuclei are quite 

 irregulär in outline. 



In the nucleus of each of the two oldest oöcytes, we find that 

 a change has taken place which connects the younger ones we have 

 described in otlier stages (Fig. 36), with the oldest one of the next 

 ovary (Fig. 49). The nucleolus is present, containing two or three 

 large and a great many small, vacuoles, which almost fill it, Dublin (7). 

 Scattered throughout or occuring in groups are a great many small 

 unstained bodies. A few of the largest of these still show within 

 them a distinct chromatin spot or spots; this is all that is left of 

 the earlier paired chromosomes. In the space left free from these 

 bodies there is a delicate achromatin fibrillar mass. 



In ovary C, we found that the paired chromosomes which are at 

 one time similar in both oöcyte and nurse-cell nucleus, broke up 

 into many pieces which became scattered throughout the nucleus. 

 In the oöcyte nucleus this change was not seen but the structure of 

 the oldest oöcyte in that stage was similar to the youngest (Figs. 29 

 to 33 oö). We now find in the pupa that, while the younger oöcyte 

 nuclei still have the paired chromosomes in them, the oldest ones 

 show a different structure. The change is not however similar to 

 what we found in the nurse-cells nuclei. In an old larva one can 

 find that a few of the paired chromosomes in the oöcyte nucleus 

 have changed to tetrads (Fig. 36) but we doubt if they all pass 

 through such a change. Each pair of chromosomes lies, as already 

 described, in a small mass of achromatin, the remains of the con~ 

 tracted thread. As new achromatin bodies appear in the nucleus, 

 some are always to be seen which are larger than the others, and, 



