56 Part second. 



and Caribbean sea form the American sponge-field. — After the removal 

 of the soft parts of the sponge the fishermen usually fill the skeleton 

 with sand, so as to increase its weight and thus to obtain a higher price 

 for their goods. For this reason it is necessary to rinse newly bought 

 sponges repeatedly so as to remove all foi-eign matter, and it is well at 

 first to add a little hydrochloric acid to the water.— The sponge of com- 

 merce is found rarely in the Bay of Naples. It chiefly frequents rocky 

 coasts and coral reefs ; it does not live in very deep waters , where its 

 elastic skeleton is of no use, nor in cold water, where we must suppose 

 that the material comjiosing it cannot be formed. — Mutilation injures 

 a sponge but slightly ; divided with a sharp razor even the smallest 

 fragments retain their life. After a time they may die , and without 

 doubt the3r suffer from the absence of the remainder of the cooperative 

 body ; under favourable conditions, however, they will live and grow. 

 Ignorant opposition of the fishermen has prevented this property from 

 being practically used. 



POLYPES (ANTHOZOA). ' 



If it be difficult to the lay mind to apply the term Sponge to organ- 

 isms , which in a living condition are not at all of a spongy nature , it 

 will l)e found equally difficult to picture as Corals anything else than 

 the beautiful red and white branches Avhich are displayed as ornaments 

 on writing-desks and chimney-pieces. And yet these branches are not 

 really tire animals themselves, but only the framework which they have 

 built themselves, and in which they live imbedded, in hundreds or thou- 

 sands, side by side or one above the other. 



Of the 2^olype.s , the animals which build up the corals , the best 

 conception may be gained by examining those kinds which are considered 

 the chief attractions of the northern Aquaria, namely the 



SEA-ANEMONES (ACTINIJ]). 



These animals exhibit a cjiindrical body , attached by an adhesive 

 disk to some fixed object and bearing- at its free end numerous very 

 mobile tentacles. These encircle an aperture, which serves both as mouth 

 and as anus (Fig. 160); it leads into a capacious stomach in which the 

 food is digested. The soft and apparently unprotected polype is really 

 very well armed. Many parts of the body, but especially the tentacles 

 w Inch serve to catch its prey, are provided with numerous microscopic 

 vesicles , the so-called stingirig-cells , each containing an 'acid liquid 

 and a spirally coiled thread. When the animal comes in contact with 

 its enemies or its prey thousands of these stinging-cells burst , ejecting 

 forcibly the long filament ; this bears a sharp point and is often barbed, 

 while the noxioiis liquid in its core renders the tiny Avound it makes 

 sufficiently poisonous to benumb or even kill. The ejection may be com- 

 pared to blowing out the fingers of a glove wiien they are tucked in. — 

 The Anemones are extremely voracious : they are not content with feed- 

 ing on the pieces of meat given them , but also catch living worms, 

 crabs, snails and fishes AAiiich are often much larger than themselves. 



