THE NATURALIST'S GUIDE. 113 



needle-like crystals of silica are to be found in greater 

 or less quantities in almost all species. 



They grow in various situations ; some few occur in 

 fresh water, but they mainly inhabit the sea. I have 

 found them encrusting rocks, pieces of shells, growing 

 on submerged posts, and one or two species I have 

 taken from the backs of the more sluggish species of 

 Crabs. A few float, or rather roll, about on the bot- 

 tom ; these usually occur in secluded bays or sounds, 

 where there is but little sea. The greater portion are 

 found attached to the bottom, often in great depths 

 of water; but many are found growing on banks, in 

 from three to four fathoms. I have also collected a 

 great many in exceedingly shoal water, near the shore. 

 I have seen thousands of the deep-water species, washed 

 ashore by the actions of the waves, during hurricanes. 



The sponges which occur in shoal water may be re- 

 moved by help of a knife ; but the deep-water species 

 are gathered with a sponge-hook, which is simply a 

 two-pronged fork, bent into a hook. The spongers of 

 the Bahama Islands and the Florida Keys use what is 

 called a water-glass, to discover the sponges on the 

 bottom. This is a cylinder of wood or metal, of about 

 ten inches in diameter, having a glass bottom. This 

 is placed in the water, bottom down, and thus the 

 operator can see the sponges quite easily through the 

 glass, even if there is a ripple on the water, which 

 would otherwise prevent his seeing to any depth. 



Sponges should be dried in the shade, without ex- 

 posing to the sun, care being taken that they do not 

 absorb dampness from the atmosphere, as then they 

 are apt to decay. 



The skeletons are procured in the following way : 

 The sponges are first exposed for a day or two to the 

 influence of the sun, then are thrown into what is 



