A rchegonium ; and on Spermatogenesis in Poly trichum. 1 1 7 
ventral canal cell therefore is not driven towards the egg-cell, and no simu- 
lation of fusion occurs. In several hundred archegonia fixed in this way , 
none showed the occurrence of the neck canal cells in the venter. It seems 
scarcely open to doubt that the abnormal conditions referred to have 
induced the fusion appearances described by J. and W. van Leeuwen- 
Reijnvaan. It will be shown later that the reduction in the number of 
chromosomes at the last division of the spermatogenic cells does not occur 
in Polytrichum formosum , the species from which the above observers’ 
figures were taken. 
The Nucleus in the Spermatogenic Cells. 
In young antheridia, shortly after the differentiation of the spermato- 
genic from the wall cells, the former cells are larger than at any subsequent 
stage. The cytoplasm is finely granular and contains numerous vacuoles 
which vary in size in different cells (PI. XIII, Figs. 1 and 3). Chloroplasts 
which seem to be in a state of disorganization also occur (Figs. 1 and 4) ; 
these persist for a few cell generations, but ultimately disappear, as they are 
not found in the cells at the time of the last division. In a single case the 
presence of well-developed chloroplasts was observed in the spermatogenic 
cells at the apex of an older antheridium, where the better illumination 
would favour their occurrence. It seems probable that they owe their 
origin to the persistence of plastids through the intervening cell generations. 
Deeply stained granules of various sizes are often found scattered through 
the cell, and each granule is usually surrounded by a clear space (Figs. 3 and 
8). The disposition of these particles is sometimes such as to suggest centro- 
somes (Fig. 3), and J. and W. van Leeuwen-Reijnvaan have figured similar 
bodies in young antheridial cells of Poly trichum formosum , and have placed 
this interpretation upon them. These observers state that they were able 
to distinguish between centrosomes and the other particles occurring in the 
cytoplasm by the presence of a clear halo which characterized the centro- 
somes. The preparations upon which the present account is based fail to 
show any distinction of this kind, and a careful search through many young 
antheridia leads to the conclusion that centrosomes are not present in the 
young spermatogenic cells, although, as will be shown later, centrosome-like 
bodies are associated with the final division of the spermatogenic nuclei. 
In the spermatogenic cells the nucleus is relatively large and centrally 
placed. Near the centre of each nucleus is a large, deeply stained body 
which sometimes has a diameter of about half that of the nucleus (Fig. 3) 
and is designated a nucleolus by most writers upon this subject. This body 
resembles the nucleolus in the root-apex of Phaseolus, as described by 
Wager ( 19 ), both in appearance and in some degree in its behaviour during 
the prophase of division. In sections stained by the triple stain the nucleolus 
is seen to consist of a central red body, probably corresponding to the 
