146 
Transactions of the Society. 
Opposed to such a hypothesis, are the observations of certain 
workers who have described the casting out of the nucleolus from 
the nucleus preparatory to mitosis. In a large amount of material, 
both animal and plant, which I have examined, I have not observed 
this occurrence during any mitosis. If such a process does take 
place, it must be exceptional, and as a 'part of the nucleolar 
material possibly remains in the nucleus, it does not seriously 
militate against this view. 
In concluding this aspect of the subject, it is desirable to point 
out that such a theory as this does not in any way involve inter- 
ference with the theory of the integral continuity of the chromo- 
somes throughout the life cycle, and also it does not assume that 
this is the only function of the nucleolus. In fact, we should 
imagine the chemical constitution of the nucleolus to be one of 
considerable complexity, and capable during metabolism of break- 
ing down to form a number of compounds of a simpler chemical 
constitution, which may play an important part in the vital 
activities of the cell. Some of this nucleolar substance may be 
extruded from the resting nucleus, and also a part may be thrown 
out into the cytoplasm during cell division, and there undergo 
metabolism. 
General Conclusions. 
Consideration of the foregoing has led me to the conclusion 
that the nucleolus, far from being a mere accumulation of waste 
products of the nucleus, has a most important part to play in the 
nutrition of the cell. It may represent elaborated enzymes, or 
the accumulation of secretory or excretory substances, which by 
enzyme action and oxidation will be broken down with the libera- 
tion of energy. Also, it is possible that it stands in some functional 
relationship to the morphological changes which take place in the 
chromosomes at different periods of cellular activity. 
As to how far each, or all of these suggestions are correct, it is 
impossible to say until more facts are available. 
Summary of the Role of the Nucleolus in the 
Germ-Cell Cycle of Limnaia stagnalis. 
A. Daring Oogenesis. 
1. In the undifferentiated cells of the germinal epithelium, there does not 
appear to be any nucleolus (fig. 1). 
2. As soon as an undifferentiated cell begins to differentiate, and grow 
into a gonocyte, an oxyphil staining nucleolus is formed in the nucleus 
(fig- 2). 
3. With growth of the oocyte, the nucleolus increases in size, performs ! 
amoeboid movements, and portions of it are extruded into the cytoplasm 
(fig. 2). 
4. When the oocyte has attained a certain stage of development, the 
