236 



Wm. S. Marshall, 



formation of the achromatin Strands which become, c/, the spireme-threads; 

 e, synapsis; f, thread which comes out of synapsis; g, shortened threads now 

 with paired chromosomes. x 850. 



Fig. 16. Three cells from the distal part of this tiibiile. Letters same as 

 last. X 1600. 



Figs. 17, 18 and 19. Three cells from same tubiile showing formation of 

 the beaded threads. x 1600. 



Fig. 20. Cell from same ovary. X 1600. 



Fig. 21. Three synapsis nuclei from near the center of figure 15. x 1600. 



Figs. 22 and 23. Cells from same tubule directly following, proximal to, 

 synapsis. The position of one of these is shown at point f, figure 15. x 1600. 



Fig. 24. A cell from the same tubule, its position indicated by g, in 

 figure 15. The paired chromosomes have appeared. x 1600. 



Fig. 25 and 26. Two cells from the same tubule showing the shortening 

 of the threads. x 1600. 



Fig. 27. Two cells from the proximal part of the same tubule. In figure 15 

 it will be Seen that this quarter of the tubule is filled with similar cells, but as 

 yet no distinction is noticeable between oöcyte and nurse cell, x 1600. 



Fig. 28. Ovary C. Longitudinal section through an ovarian tubule of 

 an older larva; in the proximal part are several groups of oöcyte and accompan- 

 ying nurse-cells. At this same end part of the stalk is drawn. x 850. 



Figs. 29, 30, 31, 32 and 33. Five oöcytes from the proximal half of this 

 tubule, each with two or three of the accompanying nurse-cells. Commencing 

 with figure 29 these are successiveley older stages and show the breaking up 

 of the paired chromosomes in the nurse-cell nuclei, and their persistance, thus 

 far, in the oöcytes. Only enough of the boundary of each oöcyte has been 

 drawn to show that it is larger than any nurse-cell. Cytoplasm not filled in. 

 X 1600. 



Fig. 34. Ovary D. Longitudinal section of a tubule from a slightly older 

 larva. No Chambers have yet been formed. x 500. 



Fig. 35. Distal part of an end Chamber from another tubule of the same 

 ovary. X 1600. 



Fig. 36. The oldest oöcyte and one accompanying nurse-cell from figure 34. 

 X 1600. 



Fig. 37. Ovary E. Longitudinal section through a tubule of a pupal 

 ovary. The terminal filament and end chamber are not drawn. x 200. 



Fig. 38. Section of the end chamber of preceding tubule. The disintegrating 

 cells, »Corps residuels«, — many labelled x — are more abundant than is 

 generally the case. x 850. 



Fig. 39. Nucleus from the oöcyte in chamber 4 of ovary E. x 850. 



Fig. 40. Same from chamber 5. x 850. 



Fig. 41. Ovary F. Longitudinal section of an ovarian tubule from an 

 older pupa. x 200. 



Fig. 42. Section of part of the terminal filament and distal half of the 

 end Chamber from another tubule of the same ovary. x 850. 



Fig. 43. Section of the proximal part of an end chamber. From the same 

 tubule as figure 41. x 850. 



Fig. 44. Oöcyte from the first, youngest, chamber of ovary F. This shows 

 the process which is often present in oöcytes of about this age, it extends 

 between the nearest nurse-cells. x 850. 



