EXPLANATION OF PLATE IX. 



Fig. I. — A portion of the sponge. Photo., nat. size. 



Fig. 2. — Vertical section, X4. 



Fig. 3.^ — Skeletal network, X45. 



Fig. 4. — Gemmule, X45. 



Fig. 5. — Gemmule, desiliciiied by means of hydrofluoric acid, show- 

 ing the poral tube, X45. 



Fig. 6. — Strongyle of skeletal framework, X 250. 



Fig. 7. — Amphidisk, x 700. 



Fig. 8. — Microstrongyle, X700. 



Fig. 9. — -Strongyle with knobbed ends (amphityle), and with rough 

 surface, from Prof. Weltner's African specimen, X 250. 



Fig. ga. — End of same, X425. 



Fig. 10.— Microstrongyle of gemmule, from Prof. Weltner's speci- 

 men, X700. 



