298 FRANZ SCHRADER 
DE Stnety, R. 1902 Recherches sur la biologie et V’anatomie des Phasmes. 
La Cellule, T. 19. 
Swincie, W. W. 1917 The accessory chromosome in a frog possessing marked 
hermaphroditie tendencies. Biol. Bull., vol. 33. 
WuitnEy, D. D. 1909 Observations on the maturation stages of parthenoge- 
netic and sexual eggs of Hydatina senta. Jour. Exp. Zool., vol. 6. 
1917 The production of functional and rudimentary spermatozoa in 
rotifers. Biol. Bull., vol. 33. 
1918 Further studies on the production of functional and rudimen- 
tary spermatozoa in rotifers. Biol. Bull.. vol. 34. 
Wiuutams, C. B. 1917 Some problems of sex ratiosand parthenogenesis. Jour. 
Genet., vol. 7. 
Witson, E. B. 1909 Studies on chromosomes. V. Jour. Exp. Zool., vol. 6. 
PLATE 1 
EXPLANATION OF FIGURES 
1 Early prophase of first maturation division. 
2 Tetrads. 
3 Typical plate of first maturation, with eleven condensed tetrads. 
4 Polar view of the anaphase of the first division. 
5 Anaphase of the first division. 
6 Plate of second polar division, with first polar body at the periphery. 
Figures 26 to 29 and 36 drawn with no. 6 eyepiece and 1.5-mm. objective. 
All others drawn with no. 8 eyepiece and 1.5-mm. objective. 
