298 NATHAN FASTEN. 



DESCRIPTION OF PLATES. 



All figures in the accompanying plates were made with the aid of the camera 

 lucida. All figures, except Figs. 3-7, were made from living spermatozoa. Figs 

 3-7 are drawings of spermatozoa which were fixed by osmic acid fumes and stained 

 with Heidenhain's iron-haematoxylin and acid-fuchsin. The magnification of 

 Figs. 1-7 is 3,300 times; that of Figs. 8-33 is 1,400 times, and that of Figs. 34-46. 

 is 1,700 times. 



EXPLANATION OF PLATE I. 



FIGS, i and 2. Bottom and side views of living spermatozoa suspended in 

 crab's body fluid, b, central body; h, protoplasmic cup; v, primary vesicle; 

 T>', secondary vesicle. 



FIG. 3. Side view of spermatozoon fixed in osmic acid fumes and stained with 

 iron-haematoxylin and acid-fuchsin. b, central body; n, nuclear cup; r, radial 

 arms; i\ primary vesicle; v', secondary vesicle. 



FIGS. 4 to 7. Bottom views of spermatozoa fixed in osmic acid fumes and stained 

 with iron-haematoxylin and acid-fuchsin, showing, respectively, three-, four-, five- 

 and six-rayed types. 



FIGS. 8 and 9. Spermatozoa in sea water. 



FIGS. 10 to 19. Spermatozoa in various concentrations of sodium chloride. 



FIGS. 20 to 23. Spermatozoa in various concentrations of calcium chloride. 



