302 XXII. BEPRODUCTION OF 



always corresponds in position with the brown fleck referred to 

 above, so that we assume that each of these latter encloses a 

 nucleus. The position of the nuclei is seen particularly clearly 

 in the antheridia. In the ripening antheridium (Fig. Ill, C) we 

 can determine that almost the whole body of the spermatozoid 

 consists of nuclear substance, which is surrounded by only a thin 

 layer of cytoplasm. The whole of the protoplasm is not thus 

 used up a little, not staining with logwood, is left between the 

 spermatozoids. 



As a fixing reagent, and to some extent better than alcohol, 

 can be used 1 per cent, osmic acid, picro-sulphuric acid, boiling 

 water, or bromine vapour. Fixing with bromine vapour and 

 boiling water often gives the best results, and is especially 

 advantageous in that it does not require a subsequent washing 

 of the preparation. The preparations can afterwards be stained 

 with logwood, saffranin, gentiana-violet, or carmine, for particu- 

 lars of which see Cladophora, Spirogyra, and " Cell-division ". 

 The stained preparations are then dehydrated and decolorised by 

 50 per cent, alcohol, which is gradually replaced by absolute, 

 then cleared with oil of cloves or oil of marjoram, and mounted in 

 Canada balsam or dammar. 



In the plants left hanging in free air, after some search, will 

 be found sexual organs which have escaped from a conceptacle. 

 They appear as small olive-green drops of mucilage at the mouths 

 of the conceptacles, and in which the oospheres can be seen even 

 with a lens. If a little of this mucilage be removed with a 

 needle, and placed in a drop of sea-water on a slide in a moist 

 chamber, we shall see numerous oospheres and spermatozoids 

 still enclosed in the inner sheaths of the sexual organs, and which 

 repeat the phenomena given above. Soon, however, the anthe- 

 ridium-cases commence to empty, at one, or, less -often, at both 

 ends. The spermatozoids (Fig. Ill, G) can commence to move 

 before, upon, or not for some time after, evacuation. The move- 

 ment is very active, and may last for several hours, but usually 

 for much less. They are pear-shaped, with two unequal cilia, the 

 shorter one attached to the anterior or pointed end of the sper- 

 matozoid, and directed forwards, while the longer one is attached 

 laterally, and directed backwards. The reddish-brown fleck or 

 eye-spot is at the point of insertion of this posterior cilium. The 

 spermatozoids can be well and quickly fixed with iodine. Freed 

 oospheres may be seen surrounded by swarming spermatozoids, 



