Ill 



PHYLUM PORIFERA 



(Fig. 38, A\ or of siliceous spicules alone, or of 

 combination of spongin fibres with siliceous spicules ( 



A.EusJDongia 



B.Pachychalina 



FIG. 38. Microscopic structure of the skeleton in various sponges. A, Euspongia, 

 network of spongin fibres ; B, Pachychalina, spongin strengthened by siliceous 

 spicules ; C, Spongelia, spongin strengthened by various foreign siliceous 

 bodies, fragments of spicules of other sponges, &c. (After Voamaer.) 





