1308 THE STORY OF THE UNIVERSE 



four, which are at right angles to it, form a cross on 

 the surface, giving it a beautiful stellate appear- 

 ance. The silicious rays of one star curve toward 

 and meet the rays of the neighboring stars, and run 

 parallel with them. All the rays of all the spicules 

 are thickly invested with consistent semi-transparent 

 gelatinous matter, which binds their concurrent 

 branches together by an elastic union, and fills up 

 the angles of the meshes with softly curved viscous 

 masses. This arrangement of the spicules, free and 

 yet adhering together by long elastic connections, 

 produces a strong, flexible, and very extensible tissue. 

 The cylindrical oscular cavity within the sponge is 

 lined with nearly the same kind of network. 



When the sponge is living, the interstices of the 

 silicious network are filled up both outside and in 

 with a delicate fenestrated membrane formed of a 

 glairy substance like white of egg, which is con- 

 stantly moving, extending or contracting the fene- 

 strae, and gliding over the surface of the spicules. 

 This "sarcode," which is the living flesh of the 

 sponge, contains distributed through it an infinite 

 number of very minute spicules, presenting the most 

 singular and elegant forms very characteristic of 

 each species of sponge. A constant current of water 

 carried along by the action of cilia passes in by 

 apertures in the outer wall, courses through the 

 passages in the loose texture of the intermediate 

 sponge-substance carrying organic matter in solution 

 and particles of nourishment into all its interstices, 

 and finally passes out by the large "osculum" at the 

 top. Over the upper third of the sponge a multitude 



