232 



Wm. S. Marshall, 



in tlie younger Chambers. The contents of the oöcytes has changed 

 very much and in the tubule no transition is found between the two 

 proximal and the two distal Chambers. We find the two oldest filled 

 with deutoplasm no trace of which was seen in any of the younger 

 tubules, this fills the entire cell in the form of large, round or 

 polygonal, bodies which lie in a granulär network. The nucleus of 

 each of these oldest oöcytes is the same (Fig. 56), it is quite irregulär 

 in outline with a thick membrane. Within the nucleus are very 

 many irregulär bodies with rounded surfaces; these stain not at all 

 or slightly. They are crowded together and leave little Space for a 

 non-staining granulär mass which is loosely scattered between them. 

 No nucleolus was found in any of the oöcytes of this age. 



Summary. 



In a fairly old larva, ovary A, the first differentiation of the 

 cells has taken place and we find them either; 1, undifferentiated 

 or; 2, passing through the first stages in the development which is 

 to result in the further differentiation of oöcytes or nurse-cells. Cells 

 of the first group may either remain unchanged and become the 

 epithelial cells, or, they may pass through the same changes as those 

 öf group two. Of group one nothing more need be said. Cells of 

 the second group pass from undifferentiated cells through the following 

 forms: with large chromatin granulös in the nucleus, h\ appearance 

 of achromatin Strands and disappearance of the chromatin granulös, c\ 

 formation from these Strands of beaded spireme-threads, d; synapsis, e. 

 It does not appear that the nucleolus has anything to do with chrom- 

 atin formation. 



In the synapsis nuclei the threads stain more darkly than in 

 the preceeding stage. 



In the youngest laryae studied, ovaries A and B, mitosis occurs 

 but is seldom found in the older stages. After the oöcytes and the 

 nurse-cells have started through these changes they do not divido. 

 From synapsis beaded threads appear, these increase in thickness 

 and in each two thin chromosomes make their appearance. The 

 threads shorten and the chromosomes become shorter and thicker. 



All oöcyte and nurse-cell nuclei reach a stage in which they 

 have this structure; proximal end of ovary B, but can not yet be 

 distinguished from each other. 



The first differentiation of these two kinds of cells is in their 



