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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



(iii.) The small aperture or inhalent pore (Fig. 14, ^), 

 through which the tube opens on the outer surface of the 

 sponge. 



(iv.) Occasionally two radiating tubes communicate 

 through an opening in the wall between them. 



Fig. 14. — Tranverse section of a calcareous sponge (G-rantia ciliate) 

 magnified about two hundred and fifty diameters. The section shows the 

 cavities of four radiating tubes. The spicules are represented in the 

 three on the left, and the cells, nuclei, and eggs, are shown in the one on 

 the right. 



a. Cloaca, b, b, b, b. Cavities of the radiating tubes, c, c, c, c', c'. Tri- 

 radiate spicules projecting into the cloaca, d. The sjTicltium. e. Skele- 

 ton of tri-radiate spicules around the tubes. /. Long needle-like spicules. 

 g. Inhalent pores, i. Eggs. 



2. The needle-shaped spicules (Fig. 14,/), which are 

 arranged in bunches or stacks over the inhalent pores. 



