304 N. M. Stevens. 



EXPLANATION OF FIGURES 



(Figures reduced I from the camera drawings) 



Figs. 1 and 2. Longitudinal optical section of male (0 and female (o) primary 

 germ cells in Sagitta inflata, 7| days. 2mm-8. 



Fig. 3. Cross-section of 7| day Sagitta through one of the primary oogonia 

 (o). 1.5 mm.-12. 

 Fig. 4. Section through young ovary containing 6-7 oogonia. 2 mm.-8. 



Figs. 5 and 6. Sections through two ovaries of the same individual containing 

 16-20 oogonia. 2 mm. 6. 



Fig. 7. Section next below the ovary of Fig. 6, showing beginning of antrum and 

 oviduct (od). 2 mm.-6. 



Figs. 8 and 11. Sections of same ovary. 2 mm.-6. 



Fig. 8. Posterior section of ovary proper showing only one oogonium (o). 



Fig. 9. Next section posterior to Fig. 8, showing the fold or outgrowth of 

 mesoderm which will give rise to antrum and oviduct. 



Fig. 10 Fifth section anterior to Fig. 8. 



Fig. 11. Tenth section anterior to Fig. 10. 



Fig. 12. Cross-section of older ovary, showing the oviduct (od) as a 2-layered 

 crescent-shaped structure. 2 mm. -4. 



Fig. 13. One-half section of older ovary showing sperm-duct tissue (sd) in one 

 wing of the oviduct (od). 2 mm. -4. 



