Sollas — On Tetractinellid Sponges. 199 



Definition of Terms. 



Ectosome. — The outer layer of the sponge, not containing 

 flagellated chambers. 



Choanosome. — The " mark " or " parenchyma," distinguished 

 by the presence of flagellated chambers. 



Eurypylous. — When the flagellated chambers communicate by 

 wide mouths directly with the excurrent canals. 



Aphodal. — When they do so by narrow canaliculi. 



Collenchyme. — Gelatinous connective tissue. 



Saraenchyme. — A collenchyme in which the collenchytes or branch- 

 ing stellate cells are replaced by granular polygonal contiguous 

 cells. 



Triana. — Tetrad spicules with a differentiated shaft — forks, and 

 anchors. 



