shrimps, male and female (of the genus Spongicola) . 

 These enter when very minute and then cannot es- 

 cape because of the sieve plate over the exhalant 

 opening. Such a glass sponge, with its pair of im- 

 prisoned dried shrimps, was long used in Japan as a 

 wedding gift symbolizing the wish that the marriage 

 would see the happy couple "together unto old age 

 and into the same grave." 



The Siliceous and Horny 



SpOnOjeS (Class Demospongiae) 



There is more than one way to gain admission to 

 this big and heterogeneous class, which includes four- 

 fifths of all sponges. Members may have skeletons of 

 siliceous spicules alone, of horny fibers alone, or of a 

 combination of the two. A few genera without any 

 skeleton at all have been slipped in, but they have 

 the complex internal channels and the multiple, 

 small, round, flagellated feeding chambers character- 

 istic of the Demospongiae. 



Sponges with skeletons composed entirely of sili- 

 ceous spicules, or those which have in addition to 

 such spicules a framework of fibers, are referred to 

 as siliceous sponges (Plate 3). The ones with both 



Fresh-water sponge, SpongiUa, common in both run- 

 ning and standing waters. It may occur in either 

 branching or encrusting form. (Vermont. William H. 



Amos ) 



spicules and fibers are the most numerous of all 

 sponges. Those entirely devoid of spicules and sup- 

 ported by horny framework alone are called horny 

 sponges. In either case the horny fibers are composed 

 of spongin, a protein secretion chemically related to 

 the connective-tissue fibers of human skin. The 

 spongin is often impregnated with rock fragments 

 and other minute foreign particles, so that most horny 

 sponges are not soft enough to be of commercial use. 



The siliceous sponges are divided into two main 

 groupings. The Tetractinellida have no spongin but 

 have four-rayed spicules. They are small to moder- 

 ately sized, drably colored, rounded sponges which 

 attract little attention. Among them is TeiilUi. men- 

 tioned earlier. In the second grouping, the Monax- 

 onida, members may or may not have spongin but 

 they have one-rayed, needle-like spicules. Here are 

 found most of the common and abundant marine 

 sponges of shores and shallow waters, and the whole 

 of the relatively small fresh-water fauna. A few ma- 

 rine monaxid sponges grow in deeper waters, some 

 even at fifteen to eighteen thousand feet. 



Among the monaxids are the largest of all sponges. 

 Neptune's goblet, Poterion, and the cake-shaped log- 

 gerhead sponge, Spheciospongia. of the Gulf of Mex- 

 ico, may be 2 to 6 feet tall or broad. In the cavities 

 of one large (185,000 cu. cm.) loggerhead sponge 

 at Tortugas, Florida, A. S. Pearse once found more 

 than seventeen thousand animals, about sixteen thou- 

 sand of them shrimps of the genus Synalpheiis. 



The breadcrumb sponge, Halichondria panicea, 

 (Plate 1 ) is a cosmopolitan species, especially abun- 

 dant on all English and other northern European 

 shores and on the New England coast north to the 

 Arctic Ocean, but somewhat spottier in occurrence 

 on the American Pacific coast. It is reported also from 

 places as far apart as Alaska, Ceylon, and Nova 

 Zembla. Usually greenish in color, but also yellowish 

 or orange, patches of different color may grow side 

 by side. The fairly smooth surface is patterned with 

 more or less regularly spaced miniature "volcanoes" 

 through which the spent water issues. The colony 

 grows as an encrusting sheet in rocky clefts, under 

 rock overhangs, and under masses of brown sea- 

 weeds — in almost any firm spot that will not be ex- 

 posed for long to the sun when the tide is out. In 

 deeper water the sponge grows more massive, with 

 higher, more slender "volcanoes." On the American 

 Pacific coast it often encrusts beds of California 

 mussels and gooseneck barnacles, along with the 

 violet-colored Haliclona, which is common on some 

 Australian shores. Also splashing color across shaded 

 rocks on both sides of the Atlantic and on the Pacific 

 coast are thin, shiny, brick-red or coral-red blotches 

 of Ophlitaspongia ( Plate 47 ) . Usually more orange- 

 red are patches of Hymeniacidon, with a rough sur- 

 face that is puckered with grooves. On Atlantic 



