Graham . — Nuclear Division of Preissia commutata. 677 
3. The spireme enters synapsis, In the knot there is evidence of the 
persistency of the spireme. The chromatin bodies are prominent in the knot. 
4. As the spireme emerges from synapsis it is quite slender, and the 
chromomeres are distinct on it. 
5. The spireme shortens and thickens. It contracts away from opposite 
sides of the nucleus, occupying a broad plane, extending entirely across the 
nucleus. Its loops do not have any definite arrangement. At the time of 
the second contraction the spireme splits. The nucleolus at this time is not 
vacuolate nor does it fragment. It, however, does not stain as deeply as in 
earlier stages. It disappears suddenly when the chromosomes are being 
formed, and while the nuclear membrane still persists. 
6. After the second contraction the spireme segments. At this time the 
splitting is plainly seen. The segments shorten and thicken. 
7. Prominent hyaline caps in polar position are applied against the 
nuclear membrane in the heterotypic division. Whether spindle fibres are 
developed in these caps or not was not determined. 
8. The poles of the spindle are broad and blunt. The method of the 
splitting of the chromosomes at metaphase was not observed. At anaphase 
they are plainly two-parted. When the chromosomes reach the poles, the 
cell plate appears as a line in cross-section. 
9. The reconstruction of the daughter nuclei takes place very quickly. 
The nuclear contents have a slight reticular appearance and there is a small 
nucleolus. The nuclei soon elongate preparatory to the second division. 
Spindle fibres are conspicuous at the elongated ends. 
10. Groups of plastids lie in the cytoplasm. There may be four or 
more of these groups. Coarse strands of cytoplasm extend from the groups 
to the nuclear membrane. 
11. No centrospheres or centrosomes were found. 
I am indebted to Prof. G. F. Atkinson for his kind advice and criticism 
during the progress of the work and the preparation of this paper ; and to 
Dr. Fred McAllister for continued and helpful suggestions. 
Literature cited. 
Chamberlain, Charles J. : Mitosis in Pellia. Bot. Gaz., xxxvi, 1903, pp. 28-51, Pis. XII-XIV. 
Davis, Bradley Moore: The Spore Mother-cell of Antlioceros. Bot. Gaz., xxviii, 1899, pp. 89- 
109, Pis. IX, X. 
: Nuclear Studies on Pellia. Ann. Bot., xv, 1901, pp. 147-80, Pis. X, XI. 
Farmer, J. Bretland : On Spore Formation and Nuclear Division in the Hepaticae. Ann. Bot., 
ix, 1895, pp. 469-523, Pis. XVI-XVIII. 
— and Moore : On the Meiotic Phase (Reduction Divisions) in Animals and Plants. Quar, 
Jour. Micr. Sci., xlviii, 1905, pp. 489-557, Pis. XXXIV-XLI. 
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