16 



Z00L0Q7. 



Fig. 13.— «, lonfritudinal section through a simple calcareous sponge, showing its 

 simple central cavity; b, showing a single osculum at the top, and the many 

 mouths over the surface. After Haeckel. 



Fig. 14. 



J. 14.— MicroKcopic section of a bit of sponge. 1, canals leading to the cham- 

 bers; 2, section of the same enlarged; 3, the ciliated cells, highly magnified 

 From Llitken's Zoology. 



