114 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the neighboring body. At a little later stage (Fig. 204) the spermatid 
has become much elongated and an axial filament is present. I have 
been unable to find, at this time, any trace of a centrosome, but the 
axial filament appears to be attached directly to the nuclear membrane 
at a point nearly, or quite, 90° from the Nebenkern. ‘The small, 
less deeply staining body which was formerly applied to the nuclear 
membrane near the Nebenkern can no longer be distinguished. Prob- 
ably it has become converted into the homogeneous envelope which 
surrounds the axial filament. 
The Nebenkern now presents a very striking appearance, since one 
side stains intensely with hematoxylin. However, the staining quali- 
ties of the Nebenkern during this and later stages appears to be 
dependent on the quality of the fixation. While one side of the 
Nebenkern stains deeply in spermatids exhibiting the best fixation,— 
e. g. those lying near the follicular wall,— in the case of spermatids 
less perfectly fixed the stain is less intense, or may be absent altogether. 
Also, in material fixed in Worcester’s formol-sublimate-acetic fluid 
the Nebenkern stains lightly or not at all. 
The chromatin continues to disintegrate into finer granules, although 
the monosome still retains its characteristic structure. Somewhat 
later (Fig. 205) the finely granular chromatin is collected around the 
periphery of the nucleus, while at the center there is a lighter region 
apparently free from chromatin. However, the peripheral distribu- 
tion of the chromatin persists only a short time, for a little later it is 
seen to occupy the anterior end of the nucleus, while at the posterior 
end. there is a lighter region (Fig. 206). The chromatin, including 
the monosome, has now become converted into very fine granules, 
which stain with hematoxylin less deeply than formerly, so that, as in 
Dissosteira, the nucleus as a whole stains grayish. ‘The nucleus now 
rotates through an angle of about 90° and at the same time two minute 
deeply staining centrosomes appear at the proximal end of the axial 
filament, where it is attached to the nucleus. I have not been able 
to determine the origin of these centrosomes nor whether, indeed, they 
lie within or without the nuclear membrane, to which they are closely 
applied. Meanwhile, the Nebenkern begins to migrate toward the 
anterior end of the nucleus. The deeply staining portion has now 
spread over one side of this body, so that about one-half of the surface 
of the Nebenkern is seen to be enveloped by a deeply staining cap. 
In Figure 207 the deeply staining cap has extended over the entire 
surface of the Nebenkern, which has now become applied to the an- 
terior end of the nucleus. The further changes in the spermatids 
prea 
hae 
