478 
MONTGOMERY. 
[Vol. XV. 
series of divisions from the single original one. This division 
usually commences, then, when the form of the nucleus changes 
from the original oval to a more elongate shape. It seems 
probable that this elongation of the nucleus may directly cause 
the division of the nucleolus, since the long axis of the latter 
coincides with that of the nucleus; and were the nucleolus in 
any way fixed in position in the nucleus, the nuclear elongation 
would draw out the nucleolus and cause it to break into frag¬ 
ments. But the division of the daughter-nucleoli does not 
always take place in the direction of the long axis of the 
nucleus, so that "some other factor might be at work to produce 
this division. 
The chromatin is arranged in the form of a reticulation (Fig. 
326). The nuclei of the younger cells are usually regular in 
outline, but those of the larger ones become very irregular; 
this irregularity of the contours of the nuclei is more marked 
by fixation with corrosive sublimate than with Flemming’s fluid, 
so that it might be regarded as an artefact caused, eg ., by the 
obstacle offered to the rapid penetration of the preserving 
fluid by the dense outer (fibrillar) layer of the cytoplasm in 
the largest muscle cells. 
17. Blood Corpuscles of Doto. 
(Plate 22, Figs. 98-101 ; Plate 23, Fig. 102.) 
(These cells are usually to be found abundantly in the 
cavity of the cirratida and of the sheaths of the tentacles, 
though their number varies greatly in different cirratida. 
They lie in the meshes of the loose network of mesenchym 
cells, either singly or grouped together into bundles. I have 
been unable to find them in other parts of the body. These 
cells appear to be free mesenchym cells, with perhaps the 
function of blood corpuscles.) 
There is always a single large nucleolus, which is usually 
very large in proportion to the size of the nucleus. It varies 
in form from a perfect sphere to an elongate oval. The nucleo¬ 
lar substance is usually homogeneous, but in some cases it is 
granular (Figs. 99-102) and then it stains faintly as if it were 
