SPONGES. 



76 1 ! 



Yet, no one can form an adequate idea of the living Sponge from the dry, dead skeleton 

 which is sold under that name. Many of the species are decked with delicate colours, 

 while all are truly beautiful creatures when viewed in full life and action. They are to 

 be found widely distributed through the seas, and there is hardly a solid body on which a 

 Sponge will not grow. Sponges are generally found hanging from the iinder sides of 

 projecting rocks at some distance below the surface of the sea, or clinging to the roofs of 

 submarine caverns. Some, however, are strong, sturdy, and branched, and stand boldly 

 erect like the earth-plants which they so wonderfully resemble. 



Even the living inhabitants of the sea are liable to become the resting-places of many 

 a Sponge, and the Crustacea are often forced to bear on their shells the additional burden 

 of living Sponges and other zoophytes much more massive than their whole body. 



The true living being which constitutes the Sponge is of a soft and almost gelatinous 

 texture, to the unaided eye ; and with the aid of the microscope is found to consist of an 



Grantia eoarctdtc.. 

 (New spedes.) 



Grantio compress,?- 



aggregation of separate bodies like those of the Amoebae, some of which are furnished 

 with long cilia. By the constant action of the cilia a current of water is kept up. causing 

 the liquid to enter at the innumerable pores with which the surface is pierced, and to be 

 expelled through the larger orifices. A Sponge in full action is a wonderful sight : the 

 cilia drives the water in ceaseless torrents, whirling along all kinds of solid particles, 

 arresting those which are useful for digestion, and rejecting those which it cannot 

 assimilate. 



The reader will at once see that a creature thus composed will stand in need of some 

 solid framework on which the delicate fabric can be supported ; and on examining a 

 series of Sponges with the microscope, we find that it is mostly composed of a fibrous and 

 rather horny network, strengthened with spiculae of a hard mineral substance. The shape 

 of the spiculae is extremely variable, some being simple translucent bars, some looking 

 much like rough flints rendered transparent, others star-shaped with several points, while 

 the greater number resemble knotted clubs made of differently-coloured glass, and having 

 a lovely effect under the microscope. 



