SPONGES. 



13 



Not all of the fibrous sponges are suited for use, for in many the fibres 

 when dry are extremely brittle, and the sponge crumbles to powder in 

 the hand. The "dead man's finger" sponge 

 (Chalinula), so common along the northern 

 Atlantic coast, is an example of this. When 

 taken from the water it seems as elastic as any 

 bathing-sponge, but the fibres when dry have 

 no strength. Other forms when dry are not 

 brittle, but are lacking in elasticity. Only the 

 members of one genus (Spongia) are possessed 

 of sufficient resilience to make them of value to 

 man, and these vary considerably among them- 

 selves in this respect. 



All of the commercial sponges are inhab- 

 itants of the warmer seas, those from the 

 Mediterranean being the most valuable, those 

 from the Red Sea standing next, while the 

 Florida and West Indian forms are still coarser. 

 Even within the Mediterranean a difference 

 exists, the sponges from the Adriatic and the 

 shores of Greece ranking hio-hest. None of 

 marketable value are found in the western 

 Mediterranean, nor in the Indian or Pacific 

 oceans. 



The sponge-fishing is an important industry in many places. The 

 sponges rarely occur in water deeper than twenty fathoms, and the majority 

 are obtained in much shallower water. They are taken from the bottom 

 by means of hooks and spears on long poles, or by 

 means of divers. Occasionally dredges are used to 

 obtain the coarser kinds. After the sponges are ob- 

 tained, they need to be freed from their animal matter. 

 This is accomplished by exposing them to the air for 

 a short time, and then placing them in large tanks 

 in the sea to allow the flesh to decay. This is a 

 rather offensive operation, and no one who has ever 

 smelled a decaying sponge can doubt that sponges 

 are animals. Gradually the flesh disappears, and 

 nothing but the fibrous skeleton remains, 

 skeletons are now washed, dried, packed in bales, 

 or strung on strings, and sent to market. The sponge as we use it is but 

 a very complicated network of interlacing fibres, in which, however, we 



Fig. 12. — Dead man's finger sponge 

 {Chalinula). 



TIipqp FlG - 13. — Fibres of common 

 bath-sponge. 



