METAMORPHOSIS OF THE SPERMATIDS. 49 
division occurring in the division of the pollen mother cell preceding 
the division which gives rise to the pollen grains. 
The most marked change takes place first in the ciliferous band, 
which continues to grow in length and width, and develops kinoplas- 
mic radiations from the outer surface. These radiations sometimes 
become very prominent, reaching out nearly to the plasma membrane 
(fig. 41). In the majority of the writer’s sections, however, no prom- 
inent radiations like these can be discovered. It is not long, however, 
till small papille are formed on the outer surface of the band which 
evidently develop into cilia later (fig. 40). It may be that these pro- 
tuberances occur while the band is young and grow into the marked 
radiations later. However this may be. it is certain that in a later 
stage the radiations disappear again or are contracted to small pro- 
tuberances on the outer surface of the band. The band up to this 
time lies free in the cytoplasm of the cell about midway between the 
nucleus and surface. 
The minute structure of the band in the spermatid in Zama reminds 
one forcibly of the structure of the tail of certain animal spermatozoa. 
While the band is still short, in fact almost as soon as it can be clearly 
distinguished to have width, one edge of the band seems to be denser 
and heavier than the other edge. This is the edge on which the gran- 
ules unite. In the mature spermatozoid. however, this distinction in 
the thickness and density of the different edges of the band can not be 
plainly distinguished. 
As the differentiation progresses the band, which has meanwhile 
absorbed all of the granules of the blepharoplast. becomes greatly 
extended in length, moves out away from the nucleus and becomes 
more or less closely applied to the plasma membrane of the spermatid. 
The band by this time has increased greatly in length and in this stage 
forms from one to two turns around the cell. In its growth the band 
is always so extended that it forms a helicoid spiral. The turns. when 
viewed from the apex, always running in a direction contrary to the 
_ hands of a clock, the spiral formed by the growth of the blepharoplast 
band is thus a levotropic one. When the ciliferous band has com- 
pleted one turn around the cell it has usually taken a position on the 
equator of the cell in such a way that it completely encircles the 
nucleus of the cell. In median sections through a spermatid at this 
stage the band is seen in sections on opposite sides of the nucleus 
(fig. 42). If the series of sections of a pair of spermatids is traced 
through till the upper section is reached the surface of the single 
band will be found to stretch entirely across it above the nucleus. To 
reach this location from the point where it was organized by the 
blepharoplast granules, the band has traveled almost the entire width 
of the cell. It can be observed in this stage to be in close proximity 
to the plasma membrane, but evidently not fused with it, as the writer 
5526—No. 2—01——4 
