126 SOiTE WOXDERS OF THE SEA. 



truth in this statement, but more than an equal amount 

 of error is mixed with it. In the first place it is scarcely 

 necessary to mention that the coral-formers are not 

 insects, but creatures of an infinitely lower organisation ; 

 and, in the next place, they can only live within a very 

 limited distance of the surface of the water. 



Putting aside the systematic division of these wonder- 

 ful creatures and their productions, we will consider 

 them all as Corals, whether they be true Corals, Mad- 

 rephylles, Gorgonias, Tubipores, Alcyonidse, &c., &c., 

 and trace, as far as possible, the course of their lives, 

 and the nature of their horny or stony skeletons. 



Some of these beings are much more simple in 

 structure than the others, and we will therefore begin 

 with them. 



Supposing that we take a rather coarse sponge, 

 especially if it has been in use for some time, and 

 compare it with the common Mushroom Madrepore, we 

 must at once see that there is a marked analogy between 

 them, even though we are only looking at the dead 

 skeleton. 



In fact, if we could take a common sponge, and trans- 

 mute it into stone instead of silex, we should have an 

 object so exactly like a madrepore that it would be very 

 difficult to distinguish the one from the other. 



If we were able to procure their living investments, 

 we should see an analogy and a resemblance between 

 them, but not an identity. 



The Sponge Animal belongs to the great group of 



