SPONGE WEAVERS. 



119 



prevailing in the axis, and of the radial system 

 towards the circumference of the sponge. Again, in 

 other cases the spicules are simply and irregularly 

 dispersed over the membranous base of the skeleton; 

 and, finally, we find it simulating the form of pure 

 keratose fibre, becoming a rigid and solid flinty 

 fibrous skeleton." 



Manifestly all this arrangement is destroyed either 

 by the natural dis- 

 integration of the 

 sponge, or the arti- 

 ficial breaking up 

 by boiling in acid, 

 as above stated, 

 the cementing ma- 

 terial being de- 

 stroyed also, and 

 nothing is left but 

 a chaos of mixed 

 spicules. The only 

 method of observ- 



ing the arrangement is by cutting carefully very thin 

 sections of the sponge, and submitting them to the 

 microscope. Of whatever substance the skeleton is 

 composed, and however it may be combined, it is an 

 essential of all sponge structure, as much as the bony 

 skeleton is of the structure of a mammal or a bird. 



This skeleton must be covered with flesh, not of 



