The sex ratio and oogenesis of Pseudococeus eitri. 181 
SCHRADER, F. 1921. The chromosomes of Pseudococeus nipae. Biol. Bull. Vol. 40. 
— 1922. A study of the chromosomes in three species of Pseudococeus. Arch. f. Zell- 
forsch. Bd. 17. 
Suny, G.O. 1919. Embryology of coceids, with especial reference to the formation 
of the ovary, origin and differentiation of the germ cells, germ layers, rudiments 
of the midgut, and the intracellular symbiotic organisms. Jour. Morph. Vol. 33. 
SILVESTRI, F. 1906. Contribuzioni alla conoscenza biologica degli Imenotteri parasiti. 
I. Biologica del Litomastix truncatellus. Ann. R. Se. Agr. Portici. Vol. 6. 
— 1908. II. Sviluppo dell’ Ageniaspis fuscicollis. Ann. R. Se. Agr. Portici. Vol. 8. 
Drawings made with ZEISS equipment. Magnification: Fig. 1 to 18 = 2160: 
Fig. 19 to 24 = 1080; Fig. 25 to 26 = 2160; Fig. 27 to 82 = 500. 
Plate 2. 
Fig. 1. The five tetrads at an early stage in the maturation of the egg. 
Fig. 2. The five tetrads slightly condensed. 
Fig. 3. The five tetrads in the final stage of condensation. 
Fig. 4. Anaphase of first maturation division. 
Fig. 5. Late anaphase of first maturation division. Each dyad lying separately in a 
clear area. Outer group incomplete. 
Fig. 6. Telophase of first maturation division. Spindlerest situated between the two 
groups of dyads. 
Fig. 7a. Anaphase of second maturation division. First polar body inactive. 
Fig. 7b. Sperm nucleus in same egg. 
Fig. 8a. Telophase of second maturation division. Nuclear wall formed around one 
daughter group. Latter showing reduced number of chromosomes. 
Fig. 8b. Sperm nucleus in same egg. 
Fig. 9a. Late telophase of second maturation division, with daughter nuclei in resting 
stage. First polar body still inactive. 
Fig. 9b. Sperm nucleus in same egg, expanded to almost maximum dimensions. 
Fig. 10a. Second polar body in resting stage. First polar body forming nuclear 
membrane and showing ten chromosomes. 
Fig. 10b. Union of male and female pronuclei in same egg. 
Plate 3. 
Fig. 11. Cleavage nucleus prior to first somatic division, showing five chromosomes 
less condensed than the five others. 
Fig. 12. First and second polar bodies approaching each other. 
Fig. 13. Polar nucleus in prophase. 
Fig. 14. Fifteen chromosomes of polar nucleus not yet fully condensed. 
Fig. 15. Fifteen chromosomes of polar nucleus in metaphase. 
Fig. 16. First division of polar nucleus. 
Fig. 17. Two daughter groups resulting from first division of polar nucleus. Fifteen 
chromosomes in each. 
