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Explanation of Plates. 
(Original maginification of all drawings was 1,750 dia. This was reduced 
Vs reproduction.) 
Plate XVI. 
Fig. 1. Primary oöcyte at beginning of growth period. 
Fig. 2. Later stage showing the presence of chromatic masses in the pale 
nncleus. 
Fig. 3. Still later stage; nuclear reticulum achromatic; nucleolus and chro- 
matic masses show great afönity for hematoxylin; cytoplasm pale-staining. 
Fig. 4. Snbsequent stage in which the cytoplasm has become basophile 
in staining reaction and the chromosomes have become massed into a single 
group or closely-wound spireme. 
Fig. 5. Oöcyte near culmination of growth period showing a compact 
chromosome-mass characteristically dose to the nuclear w'all. Cytoplasm again 
pale-staining (contains numerous yolk-sphernles). Nuclear reticulum pale and 
nonchromatic. 
Fig. 6. Typical full-grown oöcyte, showing reticular chromosome-mass 
dose to nuclear wall and to nucleolus. 
Fig. 7. Stage showing the disentanglement of the chromosome-mass and 
passage of the chromosomes into the spindle. Chromosomes are shown detach- 
ing themselves from the residual portion of the original chromosome-mass. 
Fig. 8. Later stage in the formation of the first maturation spindle ; chro- 
mosomes are small rings; remnant of original chromosome-mass seen on spindle; 
residual substance of nncleus indicated on right. 
Fig. 9. Slightly earlier prophase of first maturation mitosis showing typical 
character of chromosomes (irregulär chromatic masses), nuclear reticulum (close- 
meshed and chromatic) and nucleolus at this stage. Remnant of chromosome- 
mass shown below the spindle at point of intersection of astral rays. 
