NUCLEAR DIVISION. 5 
the nucleus, which stain deeply, closely resembling the chromatin 
granules. In the meantime the chromosomes increase in size, and it 
seems reasonable to suppose that the nucleolar substance contributes 
materially to their growth. The development of the nucleolus in the 
daughter nucleus and its behavior during the following, or second 
mitosis, seem to strengthen this theory. The chromosomes, when 
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Fic. 2.—Spindle and telophase of first mitosis in the tetraspore mother-cell of Dictyota dichotoma. 
E, spindle nearly mature; nuclear membrane has disappeared at poles. 
F, mature spindle; the small lumpy chromosomes are regularly arranged in equatorial plate; nuclear 
membrane persists at sides, 
G, daughter nuclei still connected by strand of connecting fibers; at poles of each nucleus is a well- 
developed centrosphere, 
arranged in the equatorial plate, appear, especially when crowded to- 
gether—a phenomenon of frequent occurrence—as rounded lumps 
(Fig. 2, E, F). A careful study in favorable cases shows clearly that 
each chromosome is either in the shape of a ring, or so contracted as 
to leave scarcely any central space, such, for example, as occurs in 
some higher plants (Podophyllum, Helleborus). In such cases each 
