SPONGID^. 



31 



of Spongilla solely consists of amorphous non- 

 ciliated amcebiform bodies. But it is right to 

 mention that the structure of these last is as- 

 serted by Lieberkiihn to be not quite so simple 

 as some naturalists have supposed. 



Fig. 6. 



Structure of Grantia, &c. : — a, b, c, siliceous spicula of Hali- 

 chondria ; d, portion of Grantia compressa, showing arrange- 

 ment of triradiate (calcareous) spicula ; e, smaller portion oS 

 the same (more highly magnified), showing ciliated amoebiform 

 particles. 



2. Form and l§ize. — The various kinds of 

 Sponges present themselves to our notice under 

 every possible diversity of size and outward 

 configuration. Some form flattened incrustations 

 investing the surfaces of rocks, shells, and various 

 submarine objects ; others occur as dense compact 

 masses, often of considerable dimensions; others, 

 again, are erect, cup-shaped ; while not a few 

 assume the aspect of branching arborescent struc- 



