230 
Katharine Foot and E. C. Strobell, Amitosis in the Ovary etc- 
Plate XVm. 
+ 600. 
Photos 58 — 72. Germinal vesicles in the early stages of development. As 
some of the germinal vesicles which had reached their maximum growth were too 
large to be included in the photographic field at a magnification of one thousand 
diameters, we photographed all these nuclei at a magnification of six hundred dia- 
meters to facilitate a comparison of the different stages. 
Photos 58 — 61 inclusive show relatively large nuclei with an undifferentiated 
condition of the chromatin, these later developing to the stage of differentiation (lepto- 
tene) shown in photo 68. 
Photo 62. A group of very young oöcytes. Each cell is intact, the cytoplasm 
and nucleus being distinctly demonstrated. At this stage the chromatin shows no 
structural differentiation characteristic of the leptotene stage, which appears first in 
the stage shown in photo 65. The larger oöcyte in the centre of the group of photo 62, 
with its increased amount of cytoplasm, justifies the interpretation that all these 
cells are oöcytes. 
Photo 63. Four young oöcytes similar to those of photo 62. 
Photo 64. A similar young oöcyte in which the chromatin still shows no struc- 
tural differentiation. Part of the cytoplasm is intact. 
Photos 65 — 72. Germinal vesicles isolated from the cytoplasm. 
Photo 65. An example of the smallest germinal vesicle in which we liave 
found the chromatin showing the typical leptotene stage. 
Photos 66 — 72. Show progressive stages of the differentiation of the chromatin 
into chromosomes. 
Plate XIX. 
+ 600. 
Photos 73 — 80. Demonstrate the growth of the germinal vesicles with the ac- 
companying changes in the size and arrangement of the chromatin threads, changes 
which up to a certain point, seem to represent almost a complete inversion of the chro- 
matin development shown in the earlier stages. (See plate XVIII, photos 68 — 71). 
Photo 80. Shows the latest stage in which the chromatin threads can be de- 
monstrated. Beyond this stage the threads disappear completely and the germinal 
vesicle becomes homogeneous. 
Photos 81 and 82. Show the chromatin again segregating into more definite 
threads which ultimately form the maturation chromosomes. 
Plate XX. 
+ 600. 
Photos 83 — 88. These germinal vesicles demonstrate progressive stages in the 
formation of the maturation chromosomes. 
