OF CREATION. 231 



spite of the continual encroachment of the waves, and 

 in defiance of storms and external violence, have 

 always been endowed with a rapidity of increase 

 greater beyond comparison than that of the more 

 highly organized animals. These little creatures have, 

 in the lapse of ages, been enabled to build up the 

 most solid and enduring monuments, and have con- 

 structed mountains of coral limestone, which charac- 

 terise each separate formation ; and some of their 

 race continued throughout the secondary period in 

 the part of the world we now inhabit. They were 

 represented abundantly during the deposit of the 

 chalk; and a vast multitude of sponges, organic 

 bodies even less advanced in the scale of organiza- 

 tion, were spread over the sea-bottom, and appear 

 to have been destroyed from time to time by sudden 

 irruptions of chalky mud. 



The horny net-work commonly known as the 

 sponge is nothing more than the frame- work of a very 

 peculiar kind of vegetable. The whole surface of a 

 living sponge is covered with minute apertures, with 

 large ones distributed at intervals, and the water is in 

 some way made to enter the small pores in a con- 

 tinual current, which passes out again by those of 

 larger size. It cannot be doubted that these currents 

 are connected with the supply of nutrition ; but in 

 what way the current is produced, or what are the 

 actual conditions of existence, naturalists have not 

 yet been able to discover. 



The sponge as commonly known is made up of 

 horny fibres, but a large number of varieties exist, in 

 which spiculae, or little needle-shaped crystallized par- 

 ticles of flint or carbonate of lime, separated from the 



