456 Woodburn.—Spermatogenesis in Mnium affine , var. ciHaris. 
Fig. 2 2. Drawn from sperm killed while still in the antheridium. More homogeneous throughout 
than Fig. 21. The difference may be due to conditions of less rapid development at the time 
of fixation or to the different condition under which fixation took place. 
Fig. 23. Approximately the same stage of development as in Fig. 22, but the majority of the 
cytoplasm collected around a single vacuole. 
Fig. 24. Slightly more advanced condition than Fig. 23. The coiled body of the sperm 
staining homogeneously, the cytoplasm somewhat flocculent but quite evenly distributed, and cilia 
attached to a slender forward projection, doubtless the blepharoplast. 
Figs. 25-30 represent sperms which were allowed to escape into a drop of water from the 
antheridium and were killed on the slide with 2 °/ o osmic acid. Some were allowed to remain longer 
than others in the water before the osmic acid was applied. 
Fig. 25. Cilia are present and a vesicle is quite prominent in the cytoplasm. 
Fig. 26, Cilia are present and the material of the vesicle is apparently being incorporated as 
a part of the main coiled portion of the sperm. 
Fig. 27. Cilia are present. The sperm is beginning to uncoil and the vesicle is disappearing. 
Fig. 28. Almost the same condition as found in Fig. 27. A single rather large vacuole, which 
certainly corresponds to the vesicle shown in the preceding figures, seems to be losing its substance 
to the main body of the sperm. 
Fig. 29. Probably somewhat further developed than Fig. 28. The vesicle has almost completely 
disappeared, only a few fragments remaining on the inner surface of the sperm. The point of 
attachment of the cilia is very distinctly shown. 
Fig. 30. Mature sperm. No indications of the vesicle remain. The sperm has evidently been 
free in the water for a considerable length of time. 
Figs. 31, 32, and 33. Polytrichum commune. 
Fig. 31. Nucleus of an androgone just previous to the differentiation of the chromosomes. 
Chromatin, probably in spireme condition, wrapped in a rather close knot. 
Fig. 32. Differentiation of chromosomes. Six projections or loops are distinguishable. 
Fig. 33. Six chromosomes just previous to the metaphase of division. 
