144 
Transactions of the Society. 
size of the chromosomes reduced to a half by mitosis, while other 
substances under the influence of the chromosomes (probably 
enzyme action) become converted into the materials of the 
nucleolus and karyolymph. It may be that the latter are secretory 
substances, or of the nature of enzymes, or even materials no 
longer needed for nuclear activities, but capable of yielding energy 
when metabolized in the cytoplasm. Whichever be the true 
explanation, and there may be elements of truth in each of these 
suggestions, there is no doubt that when the cell divides a part of 
these materials is returned to the cytoplasm from which they 
originally came, and this process is repeated with every cell 
division. Sometimes nucleolar extrusions occur during the resting 
stage of embryonic cells, but such an occurrence is related to a 
relatively higher degree of metabolism. However, in the resting 
cell where cell division is rare, or does not occur, the only way for 
the nucleolar material to reach the cytoplasm is by extrusions, and 
the higher the rate of metabolism the greater the frequency of its 
occurrence. This may afford an explanation of the absence of the 
nucleolus in inactive cells such as the undifferentiated cells of the 
germinal epithelium, of the comparative infrequency of nucleolar 
extrusions in embryonic cells, and the common occurrence of this 
process in active cells such as gland cells and nerve cells. 
(/) The Nucleolus and Morphological Changes in the Chromo- 
somes. — There is another quite possible function which the 
nucleolous may serve. It may be related to the morphological 
changes which take place in the chromosomes during cell 
division. The main facts supporting such a view as to this 
function are : — 
(a) That when the nucleus is about to divide, the nucleolus 
becomes smaller and progressively achromatic at the 
same time as the chromosomes are being formed from 
the nuclear reticulum and are becoming more chromatic 
(CP in fig. 17). 
( b ) That at the telophase of division when the chromosomes 
are spreading out to form the network of the “ resting 
nucleus/’ and losing their affinity for dyes, the nucleolus 
makes its appearance as a small oxyphil staining body 
amongst the nuclear network. It grows in size, while 
the chromosomes become progressively more dispersed 
and less chromatic (CFi, CF 2 in fig. 16). 
(c) That during the synizesis stage of spermatogenesis, the 
nucleolus is drawn towards the contracted chromosome 
complex (fig. 7), and it disappears from the nucleus as 
the definitive chromosomes of the diakinetic stage 
appear. 
Eecent researches on the nucleus have led us to regard each 
chromosome as an amoeboid body, which during the “resting 
