Wilson. — Spermatogenesis in the Bryophyta . 445 
division similar to that described by J. and W. Docters van Leeuwen- 
Reijnvaan in the antheridia of several species of Poly trichum and in Mnium 
sp. takes place in the Musci. 
The final divisions in the antheridia of the two species show, however, 
several points of interest. In Mnium hornum the axis of the spindle usually 
coincides with the longitudinal axis of the cell, and is not diagonally arranged 
as is the case in many of the Hepaticae. In a few cases, however, an almost 
diagonal arrangement was observed. At the corresponding division in 
Atrichum uudulatum , although the axis of the spindle is sometimes almost 
diagonal, it is usually parallel to the longitudinal axis of the cell. The cells 
resulting from the final division in both species are, however, never triangular 
in section, but rectangular or polygonal. Since no shrinkage takes place in 
the cells before the final division, these cannot be easily distinguished from 
the spermatogenic cells at earlier stages of development. 
It is therefore doubtful whether the term ; mother-cell ’ should be 
applied to the cells immediately before the final division or to the cells 
resulting from this division. 
In the Hepaticae the mother-cells each give rise to two spermatids. 
In Marchantia and Fegatella these mother-cells can be distinguished by the 
fact that they divide diagonally, and in Pellia , Aneura , and Makinoa by 
their contraction before the final division. It must therefore be concluded 
that either the mother-cells in the Musci do not divide, and only one sper- 
matid is produced in each, or that at their division the axis of the spindle 
is generally not diagonal. Since divisions of approximately the diagonal 
type are sometimes found, it appears that the second of the above possi- 
bilities may exist. The occasional occurrence of such divisions might be 
adduced as evidence for the Hepatic ancestry of the Musci, but in view of 
the irregularity in shape of many of the spermatogenic cells, too much 
importance must not, perhaps, be attached to this fact. The discovery of 
* double ’ spermatids in Mnium hornum can be cited as additional evidence 
for the formation of two spermatids from each mother-cell in this plant. It 
may also be pointed out in this connexion that the production of two male 
cells from each mother-cell is almost universal in the Pteridophyta, Gymno- 
spermae, and Angiospermae. 
Several different structures have been described in the developing 
spermatozoid in the various groups of plants. The most important of these 
is the blepharoplast, and this is the only one which is constantly found in 
the spermatid at some stage in its development. A considerable literature 
has appeared dealing with the formation of this body. Four methods of 
origin have been assigned to it in various plants. 
I. In a large number of cases the blepharoplast is said to arise de novo 
in the cytoplasm, either in the spermatid itself or in the spermatogenic cell 
before its final division. It is said to originate in this manner in Cycas 
