TEC 
SPERMATOGENESIS OF EUSCHISTUS (a9 
half of the sphere (Pf) which had previously stained faintly now 
stains deeply, which might imply that the discharged nuclear 
substance had combined chemically with that portion of the 
sphere. Yet against such an interpretation it is to be remarked 
that the nuclear discharge seems always to be effected on that 
side of the centriole (c) directed away from the sphere (Sp, 
figs. 131 to 134). This matter was also studied by me in living 
sperm and in them I was able to find all the appearances shown in 
the drawings of fixed and stained material, though in life I could 
neither see the nucleus becoming visibly smaller nor see any 
substance passing out of it. Therefore the temporary withdrawal 
of the envelope of chromatin from the centriolar pole and the 
diminution of nuclear volume is an entirely normal process, in 
no way an artefact; and in life, quite as clearly as in sections, is 
to be seen the condition of fig. 135, with one pole of the nucleus 
quite clear as though substance had passed out of it, a condition 
in marked contrast to that of figs. 125 to 1380. There is some 
doubt as to the nature of the discharged nuclear material, especi- 
ally since no definite trace of it persists in the cytoplasm and there 
is no evidence that it is thrown out of the cell. But there is some 
indication that the idiochromosome is ‘at this time either elimi- 
nated from the nucleus, or else changes its nature to such an 
extent that it can be no longer distinguished. For, omitting from 
consideration the appearances of discharge shown in figs. 131 to 
134 it is remarkable that after the nucleus has shrunken in size 
(figs. 135 to 147) it never shows a trace of the large granular idio- 
chromosomes. The fact is that the idiochromosome is clearly 
evident up to the time of the nuclear discharge, while after then 
it can no longer be seen. 
After the discharge from the nucleus its contents are sparse 
achromatic globules and threads (figs. 135 to 148), later very 
fine granules (fig. 144), while in the mature sperm head (fig. 147) 
the nuclear sap appears nearly homogeneous. This nuclear 
shrinkage takes place on all sperm without exception. 
