TEE COMMON FRESH-WATEE SPONGE. 
9 
Fig. 13. Oyi-bearing ‘^cell” of medulla of a gemmule. 
„ 14. Elongated nucleated cell/’ with a smooth spicule forming in its 
interior. 
„ 15-16. Smooth spicule partly developed. 
„ 17. Young Spongilla developed from a gemmule : a, investing mem- 
brane ] h, bundles of spiculs detaching investing membrane 
from medullary mass ; c, apertures in investing membrane ; 
d, medullary parenchyma ; e, efferent canals j f, afferent canals ; 
g, common outlet of efferent canals ; h, remains of gemmule 
(after Carter). 
,, 18. Portion of investing membrane of fig. 17 : a, muricated spicule j 
h, leaf-like cells ; c, afferent aperture in membrane, open ] dj 
ditto, partly closed ) e, ditto, closed, 
„ 19. Free pedunculate cell,” or sarcoid of Spongilla : a, aqueous 
currents (after Carter). 
„ 20. Uvella-like group of sarcoids (Carter). 
„ 21. Actinonhrys form assumed by portion of Spongilla (Carter). 
