PORIFERA 



119 



Cliona (Monaxonida^). A cosmopolitan genus, which bores into 

 the shells of molluscs and into calcareous rocks. 



Halichondria^ the crumb -of-bread sponge (Monaxonida). A com- 

 mon British littoral form, usually of encrusting growth. 



Spongilla (Monaxonida). A member of the family of freshwater 

 sponges mentioned on p. 117. Cosmopolitan. 

 A der.c. B 



Fig. 105. A, Larva {Amphiblastula) of Sycon raphanus. B, The same larva 

 with flagellated cells invaginating. After Schulze. ca. segmentation cavity; 

 der.c. dermal cells; fl.c. flagellated cells. C, Section of flagellated chamber 

 of Spongilla lacustris, showing collar cells. From Vosmaer. ap. apopyle; nu. 

 nucleus; vac. vacuole. 



Euspofigia, the bath sponge (Keratosa). Mediterranean, West 

 Indies, etc. 



Hippospongia (Keratosa). A sponge of the same kind with a coarser 

 texture due to the inclusion of much foreign matter in its skeleton. 



Oscarella (Myxospongiae). British, has no skeleton. 

 ^ See legend to Fig. 102. 



