VITAL CAUSES OF CHANGE. 2?U 



CHAPTER X, 



Coral Animalcules. 



"Deep in the wave is a coral grove, 



Where the purple mullet and gold-fish rove 

 Where the sea-flower spreads its leaves of blue 

 That never are wet with falling dew, 

 But in bright and changeful beauty shine, 

 Far down in the green and glassy brine." 



PercivaL 



WE now enter upon a most interesting branch of our subject, 

 the influence of organic action in producing change, and we will 

 soon find that of all agents which at the present moment are form" 

 ing rocks, the most remarkable are those minute and fragile ani- 

 mals termed Coral Animalcules. A vast number of islands in 

 the Pacific, Indian, and Atlantic oceans are entirely composed of 

 the calcareous skeletons of these minute animals, and they are at 

 the present moment rapidly increasing in their extent. Straits 

 and seas, once easily and safely navigable, are now rendered ex- 

 tremely dangerous, and even impassable. It will not be unpro- 

 fitable or uninteresting to devote a short space to the considera- 

 tion of these wonderful specimens of organic existence. 



The nature of coral animalcules is but little understood by most 

 persons, they suppose that the hard calcareous substance called 

 coral, is a part of the animal itself, this, however, is not the case. 

 The stony substance, may be compared to an internal skeleton, 

 for it is surrounded by a soft animal investment, capable of ex- 

 panding, and when alarmed, of contracting and drawing itself 

 almost wholly into the hollows of the hard coral. Though often 

 beautifully colored in their own element, yet when taken out of 

 the water they appear like a brown slime spread over the stony 

 nucleus. The coral animalcule*, exist in a great variety of forme 



