CHAP, ii.] THE CRUISE OF THE 'LIGHTNING.' 73 



and finally passes out by the large c osculum ' at the 

 top. Over the upper third of the sponge a multitude 

 of radiating rigid silicious spicules form a kind of 



ornamental frill, and from the lower third a perfect 



; maze of delicate glassy filaments, like fine white hair, 

 spread out in all directions, penetrating the semi-fluid 

 mud, and supporting the sponge in its precarious bed 



i by increasing its surface indefinitely while adding 



. but little to its weight. 



This is only one of the ways by which sponges 



i anchor themselves in the ooze of the deep sea. 

 Hyalonema sends right down through the soft 

 mud a coiled whisp of strong spicules, each as thick 

 as a knitting needle, which open out into a brush 

 as the bed gets firmer, and fix the sponge in its place 



| somewhat on the principle of a screw pile. A very 

 singular sponge from deep water off the Loffoten 



i Islands spreads into a thin circular cake, and adds 



i to its surface by sending out a flat border of silky 



; spicules, like a fringe of white floss- silk round a 

 little yellow mat ; and the lovely Enplectella, whose 

 beauty is imbedded up to its fretted lid in the grey 



i mud of the seas of the Philippines, is supported by 



i a frill of spicules standing up round it like Queen 



; Elizabeth's ruff. 



The sponges of the deep-water ooze are by no 



I means confined to one group. The Hexactinellidce 

 are perhaps the most abundant, but corticate sponges 



j even, closely allied to those which look so rigid when 

 fixed to stones in shallow water, send out long anchor- 

 ing spicules and balance themselves in the soft mud 

 (Fig. 7) ; and off the coast of Portugal Mr. Gwyn 

 Jeffreys dredged in 1870 several small forms of 



