STRUCTURE AND FORM OF THE MATURE SPERMATOZOID. 51 
spermatozoid in section. The plasma membrane over the band is 
strongly indented both in spermatids before motion has started (fig. 45) 
and in the spermatozoids swimming free. This forms a deep helicoid 
furrow on the outside of the spermatozoid body. Below this inden- 
tation lies the ciliferous band, frequently in such close connection 
with the plasma membrane that it is difficult to determine that the 
band has not fused with it. In some instances, however, in the most 
mature specimens, it can be seen that the band remains distinct and 
that the very numerous cilia growing from it penetrate through the 
plasma membrane (fig. 46). 
An interesting question is presented in regard to the structure of 
the ciliferous band. In some sections it would seem to be made up of 
numerous fine granules placed together side by side in such a way as 
to form a connected membrane, and the cilia appear to grow from 
these granules. It would be interesting to know if these individual 
granules are the same granules in each case as occurred before the 
organization of the band when the blepharoplast had broken up into 
a mass of granules. While this would seem probable and a natural 
sequence, no direct evidence has been discovered in its support. It 
might be added that the number of cilia on the band would seem to be 
larger than the number of granules in the blepharoplast, but no actual 
estimation of the number of these has been made in either case. The 
development of the cilia from definite granules in the band can be 
analogized with the granules which Strasburger found at the base of 
the cilia in the swarmspores of Zdogonium Vaucheria, ete. (112). 
Another feature of importance in the spermatozoid formation of 
Zamia is the metamorphosis of the entire spermatid cell into a sper- 
matozoid. In the writer’s preliminary papers it was pointed out that 
when the central cell divides to form the spermatids a plasma mem- 
brane is formed entirely across the cell, and that in the transformation 
of the two daughter cells or spermatids into the spermatozoids these 
cells are transformed directly into the spermatozoids without the for- 
mation of a new plasma membrane. There is thus no formation of 
the spermatozoids inside of a mother cell and the differentiation of 
new walls around the spermatozoids, as had been described in all pre- 
vious cases of spermatozoid formation, so far as known to the writer. 
The correctness of the writer’s observations were questioned by some 
botanists, and this has led hin, in later investigations, to give special 
attention to this point. Further study, however, has only confirmed 
the view first stated. The spermatids are made up of the entire daugh- 
ter cells resulting from the division of the central cell. The correct- 
ness of the writer’s observations on this point were confirmed by Ikeno 
in his study of the spermatogenesis of Cycas (70), where no mother- 
cell membrane or wall inclosing the spermatozoids was found. In 
Ginkgo the matter still remains in doubt. Hirase (62) does not dis- 
