338 PRE-DETERMINATION IN NATURE 



transverse rods soldered together. In other cases there were four- 

 rayed or six-rayed needles of silica, with their points attached 

 so as to form a beautiful lattice-work, with its meshes eitker 

 square or lozenge-shaped. For protection sharp needles were 

 arranged like chevaux defrize at the sides and apertures, and 

 these last were sometimes covered with a hood or grating of 

 needles, to exclude intruders from the interior cavity. Other 

 species, however, like some in the modern seas, seemed to despise 

 these niceties, and contented themselves with long straight 

 needles placed in bundles, or radiating from a centre, and thus 

 supporting and protecting their soft and sensitive protoplasm. 



Curiously enough, these old sponges did not avail them- 

 selves of the natural cystallization of silica, which, left to itself, 

 would have formed six-rayed stars, with the rays at angles of 

 sixty degrees, or six-sided plates, rods, or pyramids. They 

 adopted another and peculiar form of the mineral, known as 

 colloidal silica, and being thus relieved from any need to be 

 guided by its crystalline form, treated it as we do glass, and 

 shaped it into cylindrical tubes, round needles and stars or 

 crosses, with the rays at right angles to each other. 



The sponges whose skeletons are thus constructed, and which 

 anticipated so many mechanical contrivances long afterwards 

 devised by man, belonged to a group of silicious sponges 

 {Hexadinelltdce) which is still extant, and represented by 

 many rare and beautiful species of the deep sea, which are 

 the ornaments of our museums, and of which the beautiful 

 Eupleectella or Venus flower-basket, from the Philippine Islands, 

 and the glass-rope sponge {IIyalo7tema), from Japan, are 

 examples. But contemporary with these there was another 

 group {Lithistidce), constructing skeletons of carbonate of lime, 

 and which preferred, instead of the regular mechanical struc- 

 tures of the others, a kind of rustic work, made up of irregular 

 fibres, very beautiful and strong, but as a matter of pattern and 

 taste standing quite by itself. If there were any sponges with 



