The celliilar elements of the Ovaiy of Platyphylax designatus Walk. 227 



in eacli of these, is a distinct cliromatin rod or dot (Figs. 39 and 40) 

 which is all that remains of the paired cliromosomes or the tetrads. 

 These we find persist through still older stages (Fig. 49). The history 

 of the niicleolus in the oöcyte nucleus differs from that in the nurse- 

 cell. Here in the oöcyte it does not change to a chromatin one, nor 

 do we as a rule find oöcyte nuclei with more than a single one 

 although some are seen with one large and one or two small ones. 

 The nucleolus first changes by becoming filled with vacuoles and 

 then, at a later stage (Fig. 49), decreases in size. 



Ovary F. This tubule is from the ovary of a pupa. In a 

 longitudinal section one can distingiüsh a small terminal filament, 

 followed by an end Chamber which, in very many tubules, is divided 

 by a small indentation into two parts. The anterior of these contains 

 a niimber of nuclei in early stages of development up to the forma- 

 tion of the paired chromosomes (Fig. 42). In the more proximal part 

 are found oöcytes and nurse-cells which are already arranged in 

 groups. Following this are the regulär Chambers (Fig. 41), small at 

 first, but, as we pass down the tubule, the cells increase consider- 

 ably in size and consequently the Chambers themselves. In this 

 tubule there are five well marked Chambers, separated, in an external 

 view, by indentations formed by a narrowing of the tubule. In sec- 

 tion the Chambers are also seen to be separated by elongated 

 epithelial cells which extend across the tubule. Fach Chamber is 

 divided into a distal part containing the nurse-cells, and a proximal 

 portion within which lies the oöcyte; between these there is no 

 distinct separating part. In all the Chambers a well defined layer 

 of epithelial cells surrounds the oöcyte, but, along the margin of 

 that part in which lie the nurse cells, one sees only a few epithelial 

 nuclei. 



To show the relation of the cells to each other three views are 

 given: Ist, (Fig. 42) most of the terminal filament and the distal 

 portion of the end Chamber; 2nd, (Fig. 43) the other, proximal, part 

 of the end Chamber; 3rd (Fig. 41) the remainder of the tubule 

 showing the five Chambers. The second and third of these drawings 

 were from the same tubule, but the first from another one of the 

 same ovary. 



The terminal filament (Fig. 42) is composed of a single row of 

 cells, these are nearly Square at its tip but they narrow very much 

 towards its base. The shape of the nuclei changes with that of the 



