DIVISION OF THE CENTRAL CELL. 43 
rated into fragments or plates, a cross section in this stage showing a 
broken line. The separations in this stage, however, are yet quite 
irregular and infrequent. The content of the blepharoplast has con- 
tracted considerably, but still retains its vacuolate appearance (fig. 32). 
The kinoplasmic radiations which in the preceding stage were very 
strongly developed evidently almost disappeared at this stage, as sey- 
eral well-stained sections of nuclei in this stage show at best only 
slight suggestions of radiations. The reticulum of the protoplasm is so 
arranged as to give the suggestion of radiations immediately adjoining 
the blepharoplast. What becomes of the radiations the writer is 
unable to say. They may in some way aid in the spindle formation, 
but the nuclear membrane still remains unbroken. Wilson says that 
‘it is now generally agreed with Van Benedin that the mantle fibers 
are essentially a part of the asters—i. e., are simply those astral rays 
that come into connection with the chromosomes” (130, p. 79). This is 
certainly not the case in Zama, unless we can imagine the rays of the 
blepharoplast swinging around, losing their connection with the 
blepharoplast, and penetrating into the nucleus through a well-formed 
nuclear membrane. The mantle and interzonal fibers of the spindle 
are both formed and the spindle apparently fully developed before 
the nuclear membrane breaks down. 
As the division progresses and reaches about the metaphase the outer 
membrane of the blepharoplast becomes more plainly segmented (fig. 
61, photograph) and the vacuolated content has become more shrunken 
and is plainly disappearing. During the metaphase, or slightly before 
or after, the nuclear membrane breaks up and would appear to become 
transformed into spindle fibers, which remain in the position previ- 
ously occupied by the nuclear membrane and preserve the outline of 
the nucleus. 
In an early anaphase of division (figs. 33 and 62) the dividing nucleus 
presents a perfectly normal appearance so far as the main features of 
division are concerned. The chromosomes have just pulled apart and 
are approaching their respective poles; the nuclear membrane has dis- 
appeared, but the outline of the nucleus is still preserved by fibers 
which seem to have been formed by the disorganization of the nuclear 
membrane. The disappearance of the nuclear membrane seems to be 
gradually accomplished by its breaking down and becoming directly 
transformed into fibers of the spindle, outside of the mantle fibers, 
which spread out in each direction toward the periphery of the cell 
and later take part in the formation of the new delimiting plasma 
membrane. A layer of cytoplasm around the nucleus and a hemis- 
pherical mass of cytoplasm at each pole presents a different structure 
and staining capacity from the general mass of the cytoplasm. It is 
composed of a more open reticulum, which does not stain so deeply as 
the more dense outside portions. ‘The poles of the spindle end in this 
