The Morphology and Physiology of the Nucleolus . 141 
represents substances undergoing metabolic activities during their 
passage from the cytoplasm through the nucleus. 
Danchakoff ( 8 ) has also given an account of a similar process 
in the egg of the sea-urchin, Strongylocentrotus lividus. Towards 
the end of oogenesis there is a large well-marked nucleolus in the 
oocyte, but in the mature egg the nucleus is achromatic, and 
granules of a basophil staining substance are present in the 
cytoplasm. After fertilization, and at the beginning of artificial 
parthenogenesis, the small achromatic nucleus attracts these 
basophil granules towards it, and Danchakoff contends that they 
pass through the nuclear membrane and are converted into 
chromatin, from which the chromosomes are differentiated. 
Criticism which must be brought forward against the work of 
these two observers is that they have used no techniques for 
demonstrating cytoplasmic organs. True, Danchakoff figures what 
she calls mitochondria, but they are not at all like the well- 
defined bodies one gets by the Mann-Kopsch or Champy-Kull 
methods. When one bears in mind the earlier misinterpretation 
of the basophil substance of the frog’s egg (to which reference was 
previously made) that turned out to be mitochondria badly fixed, 
one realizes the necessity before accepting these observations, of 
further investigations on the activity of the cytoplasmic organs 
while these so-called processes of nuclear absorption are taking 
place. 
With regard to the basophil bodies which are found in the 
cytoplasm during certain stages of cell division, Tennent (57) finds 
that they are not chromidia, as several observers have concluded, 
but that they arise as the result of indirect nuclear activity. As 
to their origin he suggests that suspensoid particles which are 
surrounded by emulsoid particles, coalesce, as a result of dehydra- 
tion produced by an enzyme, which is emitted by the nucleus and 
passes into the cytoplasm. The change is reversible, and the 
basophil particles again pass into solution at a later stage of cell 
division. 
(( d ) Biochemical Considerations . — From the physico-chemical 
point of view, Moore (JfT) says we should regard the cell “ as a 
machine or mechanism through which there is constantly taking 
place a flux of energy. The cell is continually taking up energy 
from its surroundings in certain forms, and redistributing this 
energy in other forms, but in the process, it itself undergoes little 
or no permanent changes.” The chromosomes are an example of 
the stable cellular mechanism, but the nucleolus is undergoing 
continual changes. 
Of the energy changes, Moore says that the living cell can, in 
common with unorganized catalysts or enzymes, “ (a) commence a 
reaction which does not proceed at all in its absence, and (b) alter 
the velocity of a reaction which does proceed in its absence, and 
