EXPLANATION OF PLATES. 



PLATE i. 



FIG. i. Sectional view of mass of oogonia ; cell-boundaries are indistinct. X 2100. 



FIG. 2. Primary oocyte at the very beginning of the growth-period. Cell-outline indi- 

 cated by dotted line. X 2100. 



FIG. 3. Slightly later stage, showing decided increase in size of nucleus. X 2100. 



FIG. 4. Still later stage, showing increase in amount of chromatin and the characteristic 

 distribution of the same in masses along the nuclear membrane. X 2100. 



FIG. 5. Oocyte entering upon the contraction phase (synizesis, McClung). The spireme 

 appears to arrange itself in two parallel strands. X 2100. 



FIGS. 6, 7, 8, 9. Nuclei with chromatin threads in more or less complete synizesis. 

 Linin network has become indistinguishable. X 2100. 



FIG. 10. Oocyte showing the spireme in complete synizesis. X 2100. 



FIGS. II, 12, 13. Oocytes showing the first stages in the disentangling of the spireme 

 from the contraction phase. Linin network faintly visible. X 2100. 



FIGS. 14, 15. Nuclei showing still later stages in the disentangling of the spireme from 

 synizesis. Nucleoli clearly visible. X 2100. 



FIGS. 16, 17, 18. Oocytes in which appear the first indications of a transverse segmen- 

 tation of the apparently continuous spireme. < 2100. 



FIGS. 19, 20, 21. Oocytes showing a distinctly beaded character of the now discon- 

 tinuous spireme. Occasional segments clearly indicate that the spireme 

 has become double. X 2100. 



FIGS. 22, 23. Oocytes with chromosomes in form of beaded threads. A portion of 

 the spireme appears still unsegmented and double. X 2100. 



FIG. 24. Oocyte in which some of the chromosomes have become condensed into 

 irregular masses while others remain as beaded threads. X 1320. 



FIG. 25. Oocyte at slightly later stage, showing all the chromosomes in the form of 

 condensed irregular chromatic masses. There are indications of ring, V, 

 and dumb-bell shapes. Some of the chromosomes appear paired ; all have a 

 mossy or feathery outline under high magnification. X 2100. 



PLATE 2. 



FIGS. 26, 27. Young primary oocytes, showing chromosomes in various stages of trans- 

 formation from beaded threads to compact bilobed bodies. Many of the 

 chromosomes appear disposed in pairs. X 1320. 



FIG. 28. Oocyte at a somewhat later stage. Attachment to ovarian stroma shown ; also 

 the enveloping connective tissue membrane. Chromosomes have dumb- 

 bell and globular shape. Linin network conspicuous. Cytoplasm densely 

 granular and deeply staining with basic dyes. X 1320. 



FIG. 29. Primary oocyte at late stage in growth-period. Chromosomes of irregular 

 shapes scattered through the slightly chromatic linin network. Nucleolus 

 very large and homogeneous. X 7OO- 



FIG. 30. Oocyte at stage just before maturation. The chromosomes, gathered into 

 a single mass, are connected with the nucleolus by a double chromatic 

 thread. X 7OO- 



FIGS. 31, 32. Oocytes at the stage just prior to maturation. The chromosome mass 

 is in position next the cell periphery. The nucleolus and chromosome 

 mass are connected by a chromatic thread. X 700. 



FIGS. 33, 34. Oocytes in which the chromosomes are collected in a mass close to the 

 nucleolus. The puckering of the nuclear wall shows that maturation is 

 imminent. The linin network still achromatic. Chromatin appears to 

 leave the nucleolus in the form of drops. X 700. 



FIGS. 35, 36. Oocytes showing a connection in the form of a beaded chromatin thread 

 between nucleolus and chromosomes. X /oo. 



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