MUNSON: SPERMATOGENESIS OF PAPILIO. 
99 
in the manner described above. The nucleus then moves away from 
the anterior end of the sperm cell which seems at the same time to 
sever its connection with the surrounding cyst wall. The cyst then 
becomes spindle-shaped; and the nuclei of the sperm cells now occupy 
a zone near the largest part of the cyst. 
The nucleus .— Previous to this, the nucleus has been compara¬ 
tively large and spherical after its reconstruction. Now after the cells 
have severed their connection with the cyst wall, and the nuclei have 
moved down from the anterior end, it becomes small and compact. 
The chromatin takes the form of a crescent, which partly surrounds 
a large clear vacuole in the center of which there is a stainable body, 
about the size of the centrosome of earlier stages. The horns of the 
crescent-shaped nucleus sometimes point forward to the anterior end 
of the cell, sometimes backward, and sometimes laterally. Hence 
the stainable body, which I take to be the centrosome (though it may 
possibly be a nucleolus), is either anterior or posterior or lateral to the 
nucleus (pi. 14, fig. 49). 
Development of the head nurse-cell .— After the separation of the 
sperm cells from the surrounding cyst, and the transformation of the 
latter into a compressed cylinder with pointed ends, that cyst cell 
which occupies the anterior end of the cyst begins to grow rapidly 
and from now on continues to expand. Its cytoplasm which up to 
the present time has been so flattened out as to be scarcely visible, 
now accumulates around the nucleus, being in part relieved of the 
lateral pull which must exist in the early stage of the spermatoeyst 
(pi. 14, fig. 49). The nucleus, also, increases in size and assumes 
a more spherical form. 
The anterior end of all the sperm cells now becomes attached to this 
one head nurse-cell. It is in connection with this, that the later devel¬ 
opment of the head end of the spermatozoon is accomplished. As 
soon as this new- connection between the sperm cells and the head 
nurse-cell is established, the nuclei of the sperm cells leave their cen¬ 
tral position and move up close to the nurse cell, at the same time 
losing their crescent form and becoming small compact deeply stain¬ 
ing bodies (pi. 14, fig. 50). 
At this time it is difficult to determine the position of the centrosome, 
as the sperm cells are now extremely elongated and compressed, 
looking hardly larger than a hair. 
Lateral cyst cells .— As the head nurse-cell develops, the other 
