1.0 mm 



Figure 2. — Photomicrographs of fibers of the principal American commercial sponges, a. Wool 

 sponge fibers, b. Yellow sponge fibers, c. Fibers from Pepperfish Keys grass sponge, d. Fibers 

 of glove sponge from the Gulf of Mexico, e. Fibers of wire sponge from north of Cedar Keys, 

 f. Cross section of one branch of a finger sponge. 



