118 
Transactions of the Society. 
More recent workers on tissue cultures have pointed out that the 
nucleolus is in a constant state of movement. Macklin ( 38) y 
observing cells of the embryo chick, says that “ the nucleoli of the 
connective tissue type of cell are irregular in shape, often elongated, 
and vary greatly in size. In the living cell they are highly refrac- 
tive. They continuously undergo changes in shape, size and 
number during the life of the cell. Their qutline is jagged, and 
they appear to break up from time to time, and afterwards recom- 
bine. At times the nucleolus comes to be very close to the nuclear 
membrane, and it may even appear to be attached to it. It is 
probably to be regarded as a gel of varying density, the densest 
portion being represented by certain densely staining granules.” 
In nucleoli of plant cells, crystals have been described by several 
observers (4,8). 
The problem of the relation of the nucleolus to the other 
nuclear organs raises considerable difficulties. Montgomery (4%) 
considers that it is merely held tightly in the nuclear network 
like “ a ball lodged in the branches of a tree, its movements hindered 
by the intervening branches, but not immovable/’ He considers 
that it has an extranuclear origin. His conclusions are derived 
from a study of the ova of Nemerteans and the mesenchyme cells 
of Cerebratulus, in which he states that “ the nucleolus appears to 
assimilate a substance or Substances from the cytoplasm, and after 
this substance has entered the nucleus it apparently undergoes 
there a chemical change, and becomes deposited on the inner 
surface of the nuclear membrane in the form of masses of varying 
dimensions.” Opposed to this view, are the greater number of 
observers, who regard the nucleolus as arising in some way from 
nuclear elements. 
There is considerable variation in the behaviour of the nucleolus 
during cell division (35). In some cases of amitotic division the 
nucleolus is seen to divide preparatory to the division of the 
nucleus as a whole, but this mode of behaviour is not general, as 
often there is no initial nuclear division at all. 
Macklin, from observations on living cells (38), concludes that 
“ the nucleolus has no direct relationship to nuclear division during 
amitosis. It may, however, have to do with the size of the nuclear 
portions ; when these latter are equal they each contain one or 
two nucleoli of about equal size, whereas when they are unequal 
one portion, usually the smaller, may not contain a nucleolus.” 
Mitosis has been observed after amitosis, preparatory to which, 
the nuclei separated amitotically, fuse, and from this fused mass 
the chromosomes are built up. It is instructive to compare with 
this type of behaviour the part played by the nucleolus during 
nuclear fragmentation — a pathological process, occurring in the 
presence of toxins, or in the absence of an adequate supply of 
oxygen. The nucleus before fragmentation is irregular in outline 
