SPONGE 



5506 



SPONGE 



pores. Through these countless minute open- 

 ings the sea water streams in at all points, and 

 is carried into every part of the sponge's body 

 by a network of canals, or tubes. If we cut 

 through an ordinary bath sponge these branch- 

 ing canals can be seen very clearly in the 

 skeleton. 



In the inner membrane, along the canals, are 

 groups of cells provided with little lashes called 

 flagella (flajel'a), which by their constant 

 waving to and fro keep the water circulating. 

 Thus the sponge is equipped with a perfect 

 "irrigation system," by means of which the ani- 

 mal gets the food and air necessary for life; 

 for the water brings oxygen, together with bits 

 of plants and tiny living organisms, such as we 

 see when we put a drop of water under the 

 microscope. The sponge has no general stom- 

 ach to digest this food; instead, each cell se- 



flinty or glassy in appearance. The exquisite, 

 lacy Venus' s flower basket, which used to be 

 credited to skilled Chinese or Japanese crafts- 

 men, is nothing but the framework of a dead 

 glass sponge. These lime and flint skeletons 

 are composed of myriads of tiny bodies called 

 spicules, made of a substance secreted by some 

 of the cells. In the form of delicate threads, 

 slender needles, or oddly-shaped crystals re- 

 sembling snow crystals, these spicules inter- 

 twine to make the solid mesh of the skeleton. 

 Sometimes they push through the tissue and 

 cluster around the mouths of the canals, thus 

 barring out dangerous intruders. Another pro- 

 tective feature of the sponge is its very disa- 

 greeable odor, suggesting garlic a highly ef- 

 fective weapon for keeping at a distance fish 

 and other sea creatures that might otherwise 

 make a meal upon its soft substance. 



SPONGES 

 (a) Exterior of a living sponge, which appears later in the stores as (&), the familiar bath sponge. 



lects from the current whatever it needs, and as 

 the water flows out through the large outer 

 openings into which the canals empty it carries 

 away all waste matter and surplus food. 



Sponges take many different shapes, some 

 ordinary and uninteresting, others most grace- 

 ful and fantastic. The form depends to a large 

 degree upon the neighborhood in which they 

 grow, for their soft tissue is, of course, very 

 yielding. In shallow water, where there is more 

 or less disturbance, they are usually irregular; 

 those which grow in deep, quiet water are, as a 

 rule, beautifully symmetrical and often very 

 wonderful. Some sponges are thin and flat; 

 some grow like low bushes with wide-spreading 

 branches; some look like fans; others resemble 

 cups, vases, or slender cylinders. In height 

 they range from the merest fraction of an inch 

 to over three feet. 



The Skeleton. On account of the jellylike 

 substance of which the cells are composed, a 

 skeleton is very necessary to support and pro- 

 tect the animal. In some species the skeleton 

 looks like lime or white marble; in others it is 



Besides the limy and glassy skeletons, there 

 is a third class, characterized by elastic, horny 

 fibers resembling silk ; and it is this variety that 

 provides the absorbent bath sponge. 



The Sponge of Commerce. Sponges are gath- 

 ered for trade purposes in various ways. In 

 some localities, especially the Mediterranean 

 Sea, where they grow in very deep water, they 

 are collected by divers. In other places dredg- 

 ing is resorted to. The fisheries off the reefs 

 of Florida use the harpoon method. Sponge- 

 fishing crews go out in large vessels for many 

 weeks at a time. The men are sent out from 

 the ships in pairs, one to manage their rowboat 

 and the other to do the actual fishing. By 

 means of a glass-bottomed bucket the latter 

 can see to a depth of sixty or more feet; and 

 when he discovers a sponge of fair size he lets 

 down his long forked pole and dextrously 

 spears it. The sponges are spread about the 

 deck or buried in sand until the flesh decom- 

 poses, and are then thrown into small pens 

 filled with water, called kraals. From time to 

 time they are beaten to dislodge the decayed 



