PLATE 1 



EXPLANATION OF FIGURES 



Figures 1, 2, 3, 7, 9, 11, 12, 16 and 17 are drawn to the same magnification 

 (X 2290) with a Zeiss 2 mm. 1.4 n. a. apochromatic objective; figures 13, 14 and 

 15 (X 2270) with a Zeiss 1.8 mm. achromatic objective; and figures 5, 6, 8 and 10 

 (X 2490) with a Leitz jV achromatic objective; a no. 12 Zeiss compensating ocular 

 being used in all cases. 



Figures 1 to 4, 6, 7, 9 to 11, 16 and 17 prepared by Dr. H. M. Gilkey; and fig- 

 ures 12, 18 and 19 by Mr. Willard Shepard. 



1 to 6 Successive phases of the transition nuclei between the last oogonial 

 division (fig. 1) and the contraction stage. From young of female 389, fixed 

 in Zenker's fluid and stained with Heidenhain's iron haematoxylin and acid 

 fuchsin. 



7 Two nuclei in the contraction stage. Fixed in Zenker's fluid, from young 

 of female 451-6 and stained with Heidenhain's iron haematoxylin and acid 

 fuchsin. 



8 Side view of nucleus in the leptotene stage. Material from female 454, 

 fixed in Zenker's fluid and stained in Heidenhain's iron haematoxylin and 

 orange G. 



9 Lateral view of a nucleus in the leptotene stage. Material from female 

 472, fixed in Zenker's fluid and stained with iron haematoxylin and orange G. 



10 and 11 Nuclei in synaptene stage, 10 polar view, and 11 a lateral view. 

 Material from female 376, fixed in Zenker's fluid and stained with iron haematoxy- 

 lin and orange G. 



12, 13, 14 and 15 Nuclei in the pachytene stage. Material of 13 from female 

 376, and that of 14 from female 481, both fixed in Zenker's fluid and stained in 

 iron haematoxylin and orange G. Material of 12 and 15 from young at birth, 

 fixed in Flemming's fluid and stained with iron haematoxylin. Figure 12, an 

 early pachytene, and figure 14 a later, both in side view. 13 is a pole view. 15 

 a very late pachytene in which polarized arrangement of threads is lost. 



16 and 17 Nuclei in the diplotene stage. Material from young one day 

 old. Fixed in Zenker's fluid and stained with iron haematoxylin and orange G. 



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