50 
Wager . — The Nucleolus and Nuclear Division 
General Considerations. 
It is not necessary here to enter into any detailed discussion as to the 
importance of the question of the function of the nucleolus. It will be 
sufficient to point out that the part ascribed to the nucleus, and especially 
the chromatin, as the bearer of the hereditary qualities in fertilization, 
renders necessary as precise a knowledge as possible of the chemical nature 
and function of each part of the nucleus before we can come to a definite 
conclusion that any one part or parts of it is more concerned in the process 
than another. The prominence of the chromosomes at certain stages during 
the division of the nucleus led to the enunciation of the doctrine that 
the hereditary qualities are transmitted by them ; that they retain their 
individuality, more or less, in the resting nucleus ; and that they must 
be regarded as individual units having an independent existence in the 
nucleus or cell. 
The observations described in this paper show that we have in 
Phaseolus a phenomenon which, if it is found to be a widely spread one, 
must modify our conception of the significance of the chromosomes and 
nucleolus in heredity. The nucleolus is intimately bound up with the 
formation of the chromosomes, and Strasburger’s contention that it is 
only concerned in spindle or kinoplasmic formation does not hold good, 
although it is not impossible that a portion of it — the plastin or pyrenin 
of Zacharias and Schwarz — may be used up in this way. There is no 
evidence either that the nucleolus originates from the spindle-fibres as 
stated by Nemec; and Hacker’s view that it is a product of excretion 
finds no support. A portion of it persists for a long time, even up to the 
stages of metaphase and anaphase, but it seems to disappear entirely 
within the region of the nuclear activity, that is in connexion with the 
chromosomes and spindle-fibres. 
It seems clear also that the nucleolus does not originate de novo either 
from nuclear substance or from the cytoplasm. There is a definite 
continuity of nucleolar substance from mother-nucleus to daughter- 
nucleus through the chromosomes. How far this supports Zimmermann’s 
conclusion, 4 omnis nucleolus e nucleolo/ is perhaps difficult to determine. 
But if the nucleolus is simply a part of the nucleus in which nutritive 
substances are stored and perhaps partly elaborated, and not an indepen- 
dent nuclear organ, then, while there may be a definite nucleolar continuity, 
it seems to me that Zimmermann’s conclusion simply becomes absorbed in 
the larger and more important — omnis nucleus e nucleo. 
It is almost impossible to avoid coming to the conclusion that the 
nucleolus must be regarded simply as a part of the nuclear reticulum, in 
which chromatin-substance is stored for the use of the chromosomes during 
