598 Annals of the South African Museum. 



could be photographed. Fig. C shows the sperms just beginning 

 to escape ; the majority of the cilia have been withdrawn, except 

 near the pore, where a number of sperms are backing out of the 

 globoid. As they do so they move actively in endeavouring to free 

 their cilia. 



Fig. D shows a globoid with a fair number of sperms already 

 free, but the majority were still moving actively inside the globoid 

 wall when the whole mass was fixed with iodine. As the sperms 

 escape, the delicate wall of the globoid gradually becomes visible 

 (Plate XLV, F), until, as it empties, its very characteristic form shows 

 clearly (fig. 7, C); the upper surface becomes raised with the pore 

 of escape in the centre, the lower surface remaining very slightly 

 curved. The membrane is extremely delicate, and so far it has 

 never yet been possible to distinguish it until the escape of the sperms 

 is nearly complete. 



Structure of the Sperms. 



On escape from the globoid the sperms show great activity, moving 

 about rapidly as soon as they have freed their long cilia from the mass 

 of their fellows (Plate XLV, F, G). 



The sperm (fig. 7, D) is an elongated narrowly pear- or spindle- 

 shaped structure, with a long slender beak forming the anterior pole ; 

 this beak is apparently formed during escape, as in the globoid itself 

 the anterior pole of the sperm is truncate, and the beak is already 

 developed when the sperm emerges. The broader end is either 

 rounded or pointed, both forms occurring side by side ; probably the 

 form of both ends alters as the spermatozoid moves about. The 

 body of the sperm is 2-4 JJL wide, the total length 10-12 p,, with cilia 

 twice, or more than twice, that length. In the basal half is an elongated 

 chloroplast containing a single small pyrenoid. Separately the sperms 

 appear almost colourless, but in bulk they are seen to be a clear though 

 somewhat pale yellowish green. The chloroplast has much the same 

 structure as in the vegetative cell, i.e. a basal portion filling the posterior 

 end of the cell and an elongation up the dorsal side of the cell apparently 

 reaching to a short way below the base of the beak, where a small red 

 eyespot is situated. In the hollow of the chloroplast, nearly central 

 in the cell, lies the elongated nucleus, with a very small nucleolus, 

 which can only be seen in prepared sections.* Near the eyespot 

 but on the clear ventral side of the sperm are two small contractile 



* Overtoil (1889, pp. 242-243) describes the sperm of V. globator as " more highly 

 specialised " than that of V. aureus (V. minor) elongated and without nucleolus. 



