44 



ZOOLOGY. 



[S«5Ct. XI. 



Floridece) 



usually filamentous, sometimes membranaceous. 



gelatinous ; 



3. Green 



■) ; membranaceous or fila 



mcntous ; rarely liorny. 



Sponges are bodies usually adherent in irregular or 

 amorphous masses, rarely in the form of hollow reticulate 

 cones ; composed of a soft, jelly-like tissue, supported by 

 siliceous or calcareous spicules, or by horny filaments. 



Thev 



" siliceous.' 



and 



(( 



calcareous" sponges. Their soft 



organic substance is commonly diffluent, and drops from 

 the firmer basis when removed from the water, or it is 

 easily washed away. It exhibits no sign of sensibility : no 

 contraction or retraction when touched or otherwise stimu- 

 lated. The evidence of life is afforded, as in the coral- 

 lines and algae, by the flow of currents of water through 

 canals, entering by pores, and in the sponges escaping by 

 larger orifices ; and an appearance of animal life is given 

 to botii alg« and sponges by the locomotion of the 

 sporules or gemmule 





Corallines are plants coated with a calcareous covering 



either red or green when fresh, becomJng white and brittle 

 on exposure to the air. 



Corals, though called " zoophytes," are true animals ; 

 the currents which permeate them enter by " mouths," 

 always provided with a crown of feelers or seizers, called 

 tentacles, and communicating with digestive sacs or '' sto- 

 machs," into which the pores of the nutrient canals open. 

 The tentaculated mouths are called " polypes." Their 



fle 



L^ 



til em toge- 



ther into an organic whole when the coral is compound or 



; 



