386 WILSON. 
EXPLANATION OF PLATE XV. 
(Zsperella fibrexilis.) 
Fic. 9. Section: gemmules in mesoderm of parent. X 800. 
Fic. 10. Section, showing possible origin of a gemmule from a single cell. 
X 800. ; 
Fic. 11. Section: gemmules in mesoderm of parent. 
Fic. 12. Section, showing situation of young and ripe gemmules in body of 
parent. A.4. 
Fic. 13. Section: adult tissue with gemmules and cell groups. The group a 
probably derived from simple cell. X 800. 
Fic. 14. Section: adult tissue with cell group and problematical gemmule-like 
body. X 800. 
Fic. 15. Section: adult tissue with cell groups (gemmule anlages). D.4. 
Fic. 16. Section, indicating the fusion of gemmules. X 800. 
Fic. 17. Section: adult tissue with gemmules. Gemmule x has probably 
been formed by fusion. D.4. 
Fic. 18. Section through mature gemmule. D.4. 
Fic. 19. Section through gemmule of about half the full size. D.4. 
FIG. 20, 20’. Sections through immature gemmules. D.4. 
Fic. 20”. Ovarian egg surrounded by mesoderm of parent. F.4. 
Fic. 20’”. Adult tissue with two full-sized gemmules, one of which, g., is con- 
tinuous with the external mesoderm, in which is an ovarian egg, o.ov. A.4. 
