174 STKUCTURE AND ECONOMY OF DAPHNIA. 



Fig. 9. — Ovarian mass, with nucleated cells. 

 ,, 10. — Deposit of lime from carapace. 

 ,, 11. — Head of D. pulex : os., optic sac ; m., muscle of labrum ; 



m', muscle of oesophagus ; m", one of the muscles of the eye ; 



br., brain ; on., optic nerve ; g, ganglion of superior antenna ; 



g', ganglion of labrum ; ces., oesophagus ; st,, stomach ; mt.j 



mouth ; s. , dark spot ; the rest as before. 

 ,, 12. — Heart, showing slit. 



,, 13. — Ephippial egg from ovary of D. psittacea. 

 ,, 14. — Ovary of D. jjsittacea : mm., cells of matrix; om., ovarian 



masses. This is as seen immediately after the passage of 



the mature eggs into the brood receptacle. 

 ,, 15. — A more advanced condition of the ovary, showing six agamic 



eggs, containing oil-globules and granules. 

 ,, 16. — Double eye-spots in embryo of D. vetula. 

 ,, 17. — Embryo of D. psittacea highly magnified, showing sa., 



superior antennae ; ^ a. , inferior or large antennae ; Ir. , 



labrum ; md. , mandibles ; g. , large oil-globule ; mc. , green 



cells of mesoderm ; sk. , enveloping skin. 

 ,, 18. — Embryo D. psittacea, shov/ing large antennae and coiled-up 



spine, sp. 

 ,, 19. — Comb, or so-called branchial plate of D. pulex. 

 ,, 20. — Early stage of embryo of D. pulex, showing short flattened 



carapace and spine. 

 ,, 21. — D. rotunda, showing large reticulations at anterior margin, 



passing into smaller ones behind, and irregular puckerings 



where the ephippium has been cast off. 

 ,, 22. — Embryo eye of D. -pulex, Avith truncated cells and incipient 



crystalline cones. 

 , , 23. — Agamic egg of D. pulex : vm., vitelline membrane ; bl. , 



blastoderm ; g. , oil-globule, surrounded by cells. 

 ,, 24. — Section of ephippium, showing inner and outer case with 



egg- 

 , , 25. — Portion of carapace of D. rotunda, showing ///. , lines of 



fission. 

 ,, 26. — Portion of stomach of i). psittacea; m Z., soft inner membran- 

 ous lining. 

 ,, 27. — Double embryo eye of D. psittacea. 

 ,, 28. — Ex^hippium, showing cellular induration. 



