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Igog. 
EXPLANATION OF PLATES XVI-XVIII 
All the figures were made with a 1.5™™ immersion objective and ocular 12 
giving a magnification of 2130, excepting fig. 36, which was drawn under a 4™™ 
dry lens with a magnification of 400. hey were reduced 4 in reproduction, can- 
celing the enlargement due to the camera and rendering them the same size as 
they were seen in the microscope. 
PLATE XV1 
Fic, 1.—A vegetative nucleus. 
Fics. 2-4.—Three stages in the formation of the spirem from the same cyst, 
showing also the asters of the preceding division in process of disintegration. 
Fic. 5.—A large nucleus in spirem beside which is a small nucleus, derived by 
gemmation, still in the vegetative condition; from the same cyst as jigs. 6-9 and 13. 
Fics. 6-9.—The development of the spindle, from the same cyst. 
Fics. 10-12.—The contraction of the spirem around the equator of the spindle; 
nuclear een with its chromatic granules dissolving; from the same cyst. 
Fic, 13.—A young spindle with the chromatin so densely aggregated around 
the es that different parts cannot be made out; from the same cyst as jigs. 
5-9. 
Fic. 14.—A spindle at metaphase, showing three of the four chromosomes. 
Fic. 15.—Chromosomes enlarging as they divide, each of them attached to 
the pole by heavy fibers. 
IG. 16.—A polar view of metaphase, showing the four chromosomes and 
the nucleolus. 
1G. 17.—Chromosomes divided and beginning to separate 
Fic. 18.—Anaphase, showing separating chromosomes andthe heavy fibers 
Which connect them across the equator of the spindle; from the same cyst as 
figs. I ee 
IG. 19.—Anaphase; chromosomes lost in the deeply staining mass at the 
Poles; pinot fibers prominent. 
PLATE XVII 
Fic 20.—Anaphase similar to fig. 19, but remarkable for the very late persist- 
ence of the aster from the previous division. 
