400 WILSON. 
EXPLANATION OF PLATE XXII. 
(Zedania Brucet.) 
Fic. 88. Surface view. Cavities have formed in sponge, and mesoderm no 
longer extends to edge of body. A.4. 
FIG. 90. Surface view — ectodermal membrane well developed except in one 
region — central canal. <A.4. 
Fic. 91. Surface view — sponge of very irregular shape, which is, however, 
common. I-inch objective. 
Fic. 92. Vertical section of recently attached sponge — no ectodermal mem- 
brane. C.4. 
FIG. 93. Vertical section of sponge with developed canal system. C.4. 
Fic. 94. Peripheral region of same sponge — double nature of ectodermal 
membrane. D.4. 
(Zedanione foetida.) 
Fic. 95. Section through oscular papilla. X 4. 
Fic. 96. Vertical section through body of sponge. X 3. 
Fic. 97. Vertical section of adult — canal system and arrangement of skeleton. 
3-inch objective. 
Fic. 98. Section of adult — disposition of ultimate branches of canals. D.4. 
Fic. tor. Modified oxea — very common form of spicule. 
