386 WILSON. 



EXPLANATION OF PLATE XV. 

 (Esperella fibrexilis.) 



Fig. 9. Section : gemmules in mesoderm of parent. X 800. 



Fig. 10. Section, showing possible origin of a gemmule from a single cell. 

 X 800. 



Fig. II. Section : gemmules in mesoderm of parent. 



Fig. 12. Section, showing situation of young and ripe gemmules in body of 

 parent. A.4. 



Fig. 13. Section : adult tissue with gemmules and cell groups. The group a 

 probably derived from simple cell. X Soo. 



Fig. 14. Section : adult tissue with cell group and problematical gemmulelike 

 body. X 800. 



Fig. 1 5. Section : adult tissue with cell groups (gemmule aniages). D.4. 



Fig. 16. Section, indicating the fusion of gemmules. X 800. 



Fig. 17. Section : adult tissue with gemmules. Gemmule x has probably 

 been formed by fusion. D.4. 



Fig. 18. Section through mature gemmule. D.4. 



Fig. 19. Section through gemmule of about half the full size. D.4. 



Fig. 20, 20'. Sections through immature gemmules. D.4. 



Fig. 20". Ovarian egg surrounded by mesoderm of parent. F.4. 



Fig. 20'". Adult tissue with two full-sized gemmules, one of which, g., is con- 

 tinuous with the e.xternal mesoderm, in which is an ovarian egg, o.ov. A.4. 



