SEXUAL CHARACTERS—ELASMOBRANCH FISHES 255 
Pour on the slide 90 per cent alcohol to fix. Allow nearly to 
dry, but not quite (as before). Stain: Mayer’s haemalum, five 
minutes, sink in a basin of tap-water till purple. Dry all parts 
Fig. 4 Spermatozoa. A, B, of Scyllium canicula; C, spermatozoon of Raia 
(after Ballowitz). a., apical body; n., nucleus (head); m., middle piece; f., 
flagellum (tail); e., énd-piece; 1/12th inch objective. (Preparation and staining 
as explained in the text.) 
of the slide except the film. Pour on successively: 30, 70, 90 
per cent and absolute alcohol followed by xylol. Allow each 
liquid to remain on about a minute. Mount in Canada balsam. 
