390 K. MASUI: 
and appearance it is also probably not to be compared with the chromatoid 
sorpuscle described by Wırsox (13) in Pentatoma. 
IV. The Spermatids up to the Formation of tre Spermatozoa. 
After the second division the chromosomes gradually begin to disintegrate 
into minute granules and later become scattered throughout the nucleus (Figs. 
83, 84). The nuclei of the spermatids in the resting stage usually contain two or 
three large chromatin nucleoli (karyosomes) and several small chromatin masses 
(Figs. 86—88). Thus the dimorphism as regards the existence of the chromatin 
nucleolus, can not here be recognized (Figs. 85—89). STEVENS (11) in guinea- 
pig and Jorpsn (11) in opossum also state that the spermatids and the 
spermatozoa are not visibly dimorphic. 
During the resting stage of the spermatid the centrosome appears near 
the nuclear wall and is surrounded by a clear area (Figs. 87, 89, 90). 
In this stage the idiozome distinctly appears in close contact with 
the nuclear wall, and shows a clear contour and compact structure (Figs. 
86, 88, 89). Most of the mitochondria usually lie near the centrosome 
(Fig. 85). 
Tn a later stage two centrosomes become clearly visible. They lie side 
by side, and are connected by a thick filament (Figs. 87, 89). These 
two centrosomes are probably produced by division of the original one. 
With this change of the centrosome the chromatin materials begin to collect 
on the surface of the nucleus, leaving only. one or two chromatin masses 
(karyosomes) (Figs. 88—94). Simultaneously with this, the nucleus gradually 
shifts its position to one side of the cell which is destined to become the 
anterior end of the spermatozoon, while a large amount of the cytoplasm 
with the mitochondrial granules gathers together at the posterior part of cell 
body (Figs. 91, 93). 
The change of the centrosome during the formation of the sperniatozoa is 
considerably difierent from that observed in the horse. The two centrosomes 
gradually part from each other, assuming an elongated dumb-bell shape, and 
change their relative position in such a way that the axis of the dumb-bell 
comes to be situated perpendicular to the surface of the nucleus (Figs. 93, 
