437 
Wilson. — Spermatogenesis in the Bryophyta. 
deeply staining nucleolus ; the retraining portion is made up of a network 
containing very fine particles of chromatin. The cytoplasm is finely 
alveolar and contains few or no deeply staining granules. 
The first sign of approaching division is seen in the increase in size 
and number of the chromatin particles. At first a few of these attain 
a greater size than the remainder, and these are frequently found near the 
periphery of the nucleus, sometimes in actual contact with the membrane 
(Fig. 62). A little later they tend to accumulate in the vicinity of the 
nucleolus, and an irregular ring of deeply staining masses is seen around 
this body (Fig. 63). The nucleus now increases somewhat in size and 
becomes elongated and bluntly pointed at each end, while the chromatin 
begins to aggregate into short, irregular threads. 
The above appearances have been seen in antheridia which do not 
show more than twelve spermatogenic cells in median transverse section, 
but unfortunately the immediately succeeding stages have not been 
observed in these young antheridia. In the succeeding metaphase the 
spindle is well marked, the fibres converging to a point at the poles, but 
no polar radiations have been distinguished. This agrees with the observa- 
tions of Chamberlain (18), who was unable to find centrospheres in the 
development from the initial cell up to the stage where the antheridium 
shows thirty or more cells in transverse section. 
After this stage has been reached centrospheres have, however, been 
observed in the spermatogenic cells, and it is a singular fact that although 
these are apparently absent in the earlier divisions, they are here found as 
well-developed structures. These centrospheres are similar to those de- 
scribed by Farmer and Reeves (23) in the germinating spores. In these 
older antheridia the early stages of division are similar to those already 
described. Soon after the chromatin granules begin to aggregate together, 
the membrane becomes drawn out into two points on opposite sides of the 
nucleus (Fig. 64). From them distinct cytoplasmic radiations extend 
(Fig. 65), but these are not so numerous as those figured by the latter 
observers in the germination of the spores. At the centre of these radia- 
tions a small granule can in some cases be seen, but as its presence could 
not always be determined, the occurrence of a centrosome is considered 
somewhat doubtful. At the following metaphase radiations were not dis- 
covered with certainty, but here again a small granule was occasionally seen 
at each pole. 
It may be noted in this connexion, that although Farmer and Reeves 
(23) were unable to ascertain the existence of any definite particle which 
would indicate the presence of a centrosome within the centrosphere, 
Strasburger (63), after examining the same preparations, concluded that 
a centrosome was always present. The constant occurrence of this body 
in the spores increases the probability of its existence in the centrospheres 
Gg 
