THE FRESHWATER SPONGES. 181 



DESCRIPTION OF PLATE VII. 



(1) Diagi*amrnatic section of the Statoblast of S pong ilia Ca?'teri, through 

 the aperture d, showing a, inner investing membrane ; b, chitinous coat ; 

 c, crust, composed in this species of hexagonal cells as fig. e. 



(2) a, Statoblast of Spongilla Carteri ; b, curved, smooth, acerate spicule 

 of same ; c, curved spinous, acerate spicule of S. Lacustris. 



(3) a, Statoblast of Meyenia fluviatilis, showing position of spicules; b, 

 birotulate spicule of same ; c, end view of disk of spicule. 



(4) a, Statoblast of Meyenia plumosa, showing position of spicules ; b, 

 birotulate spicule of same ; c, stellate form of spicule of membrane. 



(5) a, Statoblast of Tubella reticulata, showing position of spicules ; b, 

 inaequi-birotulate, or trumpet-like spicule, of same ; c, spinous skeleton 

 spicule, forming capsular layer to the statoblast. 



(6) a, Statoblast of Parmula Batesii, showing position of spicules ; b, 

 parmuliform spicule ; c, spinous acerate spicule. 



(7) Diagrams showing development of spicules. 



Journ. Q. M. C, Series II., No. 4. 



