Osmunda claytoniana, L ., and O . cinnamomea , L. 63 
form characteristic of the free-swimming condition, and the 
nucleus of the sperm-cell is globular. 
Owing to the readiness with which the sperm-cells separate, 
even in the younger stages of the spermatozoids, the main 
points in the development of the latter may be very satis- 
factorily studied by allowing the prothallia to remain in 
water until the older sperm-cells are spontaneously dis- 
charged, and then carefully crushing the younger antheridia 
so as to liberate the younger ones. By treating these with 
a drop of dilute acetic (or better, osmic) acid and then with 
gentian or methyl-violet, as is done in studying the nuclear 
division in pollen, the nuclei are strongly coloured without 
staining the protoplasm. For permanent preparations, how- 
ever, the whole prothallium should be fixed with one per cent, 
chromic acid, and, after staining with alum-cochineal, sections 
can be made with a microtome. 
From a careful study of material treated by these methods, 
there seems no room for doubt that the whole body of the 
spermatozoid, with the possible exception of a thin film of 
cytoplasm upon the surface, is derived from the nucleus, and 
is due to a direct transformation by the nucleus into the body 
of the spermatozoid. The body of the spermatozoid stains 
uniformly, in all stages, with the various nuclear stains, and in 
no case is it in contact with the wall of the sperm-cell, but 
lies free in its cavity. Not the slightest trace of a special 
nucleus within the body, as claimed by Belajeff 1 , was to be seen. 
The cilia arise late in the process of development, and are 
derived from a zone of cytoplasm that surrounds the upper 
coil of the spermatozoid (Fig. 54 c). This was most clearly 
seen when the nearly ripe sperm-cells were treated with very 
dilute osmic acid and stained with methyl-violet. This shows 
plainly the young cilia, which are then seen to arise from the 
zone of cytoplasm by its splitting into extremely fine filaments, 
one end of which remains attached to the upper coils of the 
spermatozoid, while the other is free. 
When the ripe sperm-cells are discharged from the 
1 Berichte derDeutschen Botanischen Gesellschaft, Dec. 1889. 
