SPONGES 43 



Sponges of commerce. — The sponges that we see in the 

 drug stores are nothing but the interlaced masses of soft, 

 flexible, spongin fibers that compose the skeletons. Our 

 best sponges come from the Mediterranean, the next best 

 from the Red Sea, and a poorer quality from the Bahamas, 

 West Indies, Key West, and west coast of Florida. In 

 gathering them for market, they are pulled from the rocks 

 with pronged hooks attached to poles whose length is at 

 least as great as the water is deep. In deep waters, divers 

 go down and gather them off the rocks. After being col- 

 lected they are either exposed to the air until the soft parts 

 decay, or they are thrown into kraals, or cribs, near low- 

 water mark, and left where the tides wash through them, 

 until the fleshy parts pass away. They are then bleached, 

 dried, and sent to market. 



Relation of sponges to other animals and to their en- 

 vironment. — Sponges were originally thought to be 

 colonial Protozoa, but it has now been determined that they 

 produce eggs and that these eggs, during development, first 

 divide into two cells, these into four, these into eight, these 

 into sixteen, and from these the mature sponge finally de- 

 velops. Such a mode of development certainly excludes 

 them from the one-celled animals. At the same time, the 

 sponges are the simplest of the many-celled animals. The 

 one cell of the Protozoa does everything, but in the sponges 

 some cells gather food, other cells perform reproduction, 

 while others digest food. These different cells, each de- 

 pendent upon the other, are joined together to form an 

 organized but simple body in comparison with other met- 

 azoans. 



It is evident that the sponges could not live on land be- 

 cause they are fixed and food must be brought to them, and 



