582 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
spheres appear on the outside of and in contact with the nuclear wall, 
beautiful radiations extending from them ; they are usually diametrically 
opposite to one another. The centrospheres appear then to pull the 
nucleus into an elliptical shape ; and the chromatin becomes distributed 
in the form of a narrow equatorial band lying just within the nuclear 
membrane ; it gradually becomes more definitely fibrillar, and finally 
takes the form of eight chromosomes. The rest of the nucleus is now 
entirely free from staining substances ; it becomes more and more drawn 
out, and its wall becomes gradually thinner and finally disappears ; at 
this period the achromatic spindle is differentiated. After the separation 
of the chromosomes from the equator to form the daughter-nuclei, a 
beautiful cell-plate is formed across the achromatic spindles. The 
centrospheres appear no longer to retain their individuality within the 
cytoplasm after the formation of the daughter-nuclei. In some instances 
irregularities were observed in the process of division, occasionally the 
appearance of a third centrosphere. 
Function of the Nucleus.* — Dr. A. Zimmermann gives a very 
valuable resume of recent researches on this subject, both in the animal 
and in the vegetable kingdom. He considers it as established that there 
is the closest relationship between the nucleus and the cytoplasm, neither 
being able to carry on an independent existence without the other ; that 
the attraction-spheres probably give the first impulse towards the division 
of the nucleus ; that the nucleus is the principal agent for the trans- 
mission of hereditary properties; that the phenomena of motility and 
the division of the contractile vacuoles, and the process of respiration, 
are not necessarily dependent on the nucleus ; while different observers 
are not in accord as to the necessity of this structure for the growth of 
the cell-wall and the formation of starch. 
The questions of the exchange of material between the nucleus and 
the cytoplasm, and the formation of crystalloids, are discussed in detail ; 
and a very copious reference given to the literature of the subject. 
Growth of the Cell and Nature of the Nucleus.f — Herr E. 
Zacharias has confirmed Schwarz’s observation of the increase in size of 
the nucleus, and of the nucleolar mass, in growing sieve-tubes, hairs, 
and epidermal cells, and especially in the germinating endosperm of 
Hicinus. In the epiderm of Galanthus and Hyacinthus , the mother-cells 
of the stomates are, immediately after division, nearly the same size as 
their sister-cells ; but the latter very soon increase much more rapidly 
in siee. The nucleus of the mother-cell of the stomate is also consider- 
ably smaller, and contains a larger proportion of nuclein, than that of 
the sister-cells, and its nucleoles are very much smaller. Similar differ- 
ences occur in the male and female sexual cells. The former remain 
small, and have a small nucleus containing a large proportion of nuclein, 
aud only a small nucleole or none at all. The larger female cell, on 
the other hand, has a large nucleus containing a small proportion of 
nuclein and a large nucleole. As a general rule, active growth of the 
cell is associated with an increase in the number of the nucleoles, but a 
decrease in the proj)ortion of nuclein which they contain. 
* Bot. Centralbl., 1801, Beih., pp. 81-9. 
f Ber. Deutsch. Bot. Gesell., xii. (1894) pp. 103-8. 
