596 CHRISTIAN CHAMPY AND H. M. CARLETON 
5. Tut RELATION BETWEEN CELL SHAPE AND NUCLEAR 
SHAPE. 
It is notorious that the longer a cell, the longer (usually) 
is its nucleus. Muscle, columnar epithelium, and connective- 
tissue cells are familiar examples of this (see Pl. 23, figs. 1, 8, 
and 10; Pl. 24, fig. 2). This elongation of the nucleus is often 
due to mechanical causes. Thus, in epitheha it is sometimes 
due to mutual cell-pressure, while the long nucleus of the 
smooth muscle-fibre must be ascribed to pressure from the 
myofibrillae. Further, the nucleus shortens or lengthens as 
the fibre contracts or extends. Again, in preparations of 
amphibian intestine fixed in different degrees of distension, 
there are marked differences in the height of the epithelial 
cells and their nuclei—the two varying in length in a parallel 
ratio between certain limits. Exceptions, however, exist to 
this general rule. For instance, in the intestinal epithelial 
cells of the dragon-fly Libellula (see Pl. 24, fig. 5) the 
small oval nucleus is quite disproportionate to the elongated 
cell, 
As claimed by Martin Heidenhain (8), we must surmise the 
existence of a force which tends to push the nucleus towards 
the centre of the cell. And in view of the plasticity of the 
nucleus there can be no doubt but that this force must influ- 
ence its shape also. 
It is a fact of no small significance that the nucleus 
never comes into contact with the cell mem- 
brane, except in a few instances due to powerful 
mechanical factors, e.g. pressure from bulky cyto- 
plasmic inclusions forcing the nucleus against the cell mem- 
brane. ‘Two possibilities suggest themselves in explanation 
of this : 
(1) That the position of the nucleus is due to 
forces exerted on it by the surrounding cyto- 
plasm, forces which might conceivably be proportional to 
the mass of the cytoplasm around the nucleus. Were this so, 
nuclear shape in a cell of greater length than breadth would 
