Gates. — Somatic Mitoses in Oenothera. 1001 
while in the lower nucleus the full number could not be seen owing to 
the angle from which the lower nucleus was observed. It will be seen that 
in this figure and the following (Fig. 28) the chromosomes nearly all have 
a characteristic dumb-bell shape. This was first observed several years 
ago in other floral tissues (Gates, ’ 07 , p. 19). In Fig. 28, also, 15 
chromosomes are present and can be counted very easily. These chromo- 
somes are in the form of tiny loops, or in many cases have a median con- 
striction which gives them the appearance of dumb-bells. It will be seen 
from the figures that the size of the chromosomes varies strongly, not only 
according to the size of the cell and nucleus in which they are found, but 
according to the stage of mitosis. The mass of chromatin at the poles in 
the stage represented by Fig. 26 is frequently greater than that in the early 
telophase after the nuclear membrane has been formed. These telophase 
stages also show that the chromosomes retain their individuality as inde- 
pendent bodies during the period represented by Fig. 26, during which 
they are closely massed together. The slightly later telophase in Fig. 29 
also contains 15 chromosomes. A nucleolus has not yet appeared. 
The nucleus has grown in size (its larger size in this figure also depends 
partly upon its presence in a larger cell) ; the chromosomes also are larger, 
have mostly lost their median constriction, but are still sharply individualized. 
It is not certain that the median constriction always appears, although it is 
of frequent occurrence. The increase in size of the chromosomes appears 
to be due at first to a process of swelling, which is often accompanied 
(Fig. 30) by the chromosome becoming less deeply staining, and sending 
out processes which begin to anastomose with those of adjacent chromo- 
somes. In Fig. 30 both daughter nuclei of a nucellus cell are shown in the 
same stage of alveolization. Figs. 31-3 show other nuclei in the same 
condition. The chromosomes can still be counted, at least approximately. 
The chromatin content of the nucleus is here, as in the prophase, frequently 
coiled, though quite irregularly, round the periphery of the nucleus. Before 
this stage has been reached the new cell-wall is formed, but these stages 
can of course be easily distinguished from prophases by the comparative 
size as well as position of the nuclei and cells. 
Fig. 34 shows the two daughter nuclei in a still later stage. The 
nuclei have markedly increased in size, and their anastomosis and trans- 
formation into a threadwork has proceeded farther. The chromosomes can 
still be counted, however, the whole 15 being shown in Fig. 34 £ ; and 
the median constriction still remains in some of them. Nucleoli have also 
appeared. This telophase stage is easily distinguished from the prophase 
stages represented by Figs. 5-10, not only in the size of the nuclei but in 
the shape of the chromosomes. If Fig. 34 were mistaken for a prophase the 
dark bodies might then easily be considered ‘ prochromosomes ’. In Fig. 35, 
though the nucleus has passed still farther into the resting condition, and 
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