604 CHRISTIAN CHAMPY AND H.M. CARLETON 
oval nuclei of a very definite aspect. These nuclei are remark: 
ably stable, for they often retain their shape after the rest of 
the corpuscle has been haemolysed. Now, observation of the 
normal Avian red cell reveals little beyond a rather dark 
central portion and, often, a small invagination at both poles 
of the nuclear membrane. ‘The general appearance is such 
(see T'ext-fig. 11) as to suggest the presence of some supporting 
structure within the nucleus, though the density of the 
chromatin makes its observation difficult. But when a bird’s 
red blood corpuscles are aseptically cultivated in their own 
plasma, the nucleus slowly swells up before actual death of the 
cell occurs. As the nucleus becomes spherical, the chromatin 
becomes condensed into a single nucleolus, and an axial 
rodlet can frequently be seen under such conditions. 
10. Tua RELATION BETWEEN NUCLEOLI AND NUCLEAR 
SHAPE. 
The nucleolus remains one of the most enigmatical of the 
cell components, in spite of the attention devoted to it by 
many biologists, and by Montgomery (9) and Vigier (12) in 
particular. The nucleolus is of interest in that it often shows 
amoeboid movements and undergoes independent fission 
during the life of the cell. In these observations the term 
‘nucleolus’ is used in its widest sense, as signifying any 
condensation of nuclear material within the nucleus. Con- 
sequently, the word as employed in this paper applies to both 
karyosomes (or chromatin nuclech) and plasmosomes (i.e. con- 
densations of the oxyphil substance called plastin). Not only 
do both chromatin and plastin often occur within the same 
nucleolus, but karyosomes or plasmosomes sometimes contain 
one or more granules of unknown composition, which have 
been shown by the aid of special impregnation methods to 
divide by fission during mitosis (Carleton, 8). 
Clearly the nucleolus is often a complex structure of doubtful 
significance, and it is impossible at present to dogmatize on 
the relation of this element to nuclear shape. At the most, 
certain deceptive appearances may be cleared up. 
