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The Ohio Naturalist. 
[Vol. IX, No. 1 
EXPLANATION OF PLATE XXI. 
The drawings were made with a No. 12 compensating ocular 
and a 1-12 oil immersion objective, the original magnification 
being 2250 except figure 21 for which a No. 18 compensating 
ocular was used. The plate is reduced one-third in reproduction. 
Fig. 1. Two cells from a very young antheridium, showing cen- 
trosomes on opposite sides of the nucleus. 
Figs. 2-3. Mother star stage from a very young antheridium, with 
centrosomes at the poles. 
Fig. 4. Daughter star stage showing elongated centrosomes, from 
very young antheridium. 
Fig. 5. Great grandmother cells, or earlier, showing centrosomes on 
opposite sides of the dividing nuclei. 
Figs. 6-9. Great grandmother cells, or earlier, with centrosomes at 
the poles of the spindle. 
Figs. 10-15. A series of great grandmother cells, showing the 
appearance of the centrosomes and in some cases dark-staining asters. 
Figs. 16-20. Grandmother cells in various stages of division, 
showing centrosomes at the poles. 
Fig. 21. A grandmother cell with prominent centrosomes. 
Figs. 22-32. Spermatozoid mother cells in process of division, 
showing the same kind of centrosomes as are in the earlier divisions. 
Fig. 25 shows eight distinct chromosomes. 
Figs. 33-40. Spermatids or incipient and young spermatozoids, 
showing the increase in size of the centrosome (blepharoplast) as it is 
being transformed into an elongated cilia-producing organ. 
