Further Studies on the Ovogenesis of Sagitta. 351 
Explanation of figures. 
Plate 16. 
Fig. 1. Cross-section of an ovary of Sagitta bipunctata, showing ripe 
egg (b) in the temporary oviduct. « sperm-duct; c Ist polar spindle; 
d oocyte. ZEISS’ obj. C, oc. 4. 
Fig. 2. Section of germinal vesicle, showing currents and small 
chromosomes. ZEISS’ obj. C, oc. 6. 
Figs. 3a and 3b. Two sections of the same germinal vesicle, showing 
most of the chromosomes brought together by the currents. ZEISS’ obj. C, 
oc. 6, 
Fig. 4 Germinal vesicle breaking down at the end where the spindle 
is forming. ZEISS’ obj. C, oc. 6. 
Figs. 5—8. Successive stages in the dissolution of the germinal 
vesicle and formation of the Ist polar spindle. Fig. 5, Zeiss’ obj. C, 
oc. 6; Fig. 6, Zeiss’ obj. D, oc. 6; Figs. 7—8, Zeiss’ obj. 1.5, oc. 4. 
Fig. 9. Section showing sperm-duct (c), a part of a ripe egg (e) 
with degenerating accessory cells (b) on the egg-membrane which has closed 
under them, and the opening (a) left by the breaking away of the accessory 
cells. ZEISS’ obj. D, oc. 4. 
Figs. 10a and b. Similar but slightly earlier stage than Fig. 9. c and 
d degenerating accessory cells. ZEISS’ obj. D, oc. 4. 
Fig. 11. Cross-section of Sagitta elegans, showing one ripe egg just 
entering the oviduct (a), and another wholly in (0). Egg b shows two 
polar spindles end to end. c sperm-duct. Bausch & LomB obj. 1 in. 
oc. C 
Fig. 12. Cross-section of an ovary of Sagitta elegans, showing one 
egg (a) in the oviduct and another (b) entering. Both eggs contain the 
first polar spindle in equatorial-plate stage and tangential position. ZEISS’ 
obj. AA, oc. 6. 
Fig. 13. Two chromosomes showing the preliminary longitudinal split 
which occurs during the growth stage of the oocyte. ZEISS’ obj. 1.5, oc. 6. 
