SPONGES. 35 



beneath the shelter of the Fucus-growth, will reward us with a 

 little spherical sponge with tubular oscula at the summit 

 formed of spicules, and its general surface bristling with long 

 spicules. This is the Grantia ciliata, looking like a little 

 gooseberry. 



There are many other forms, for 

 which I must refer my readers to 

 Dr. Bowerbank's work, where also 

 be found descriptions and 

 figures of many deep-water spe- 



tional sponge-like Chalina oculata, 

 in branching masses nine or ten inches high. 



There is, however, one other we must mention ; .the so-r 

 called Boring-sponge (Cliona celata), which attacks various 

 shells and stones. It is quite a common occurrence for the 

 rambler along the shore to pick up the shell of some mollusk, 

 and find it so tunnelled, the borings branching in every direc- 

 tion, that what would otherwise be as strong as stone is now 

 as weak as poor strawboard, and will yield to very slight 

 pressure or strain. On breaking such a shell across we get 

 both cross and longitudinal sections of these tunnels and 

 chambers, and find some of them to be lined with a dark- 

 brown filmy tissue, the remains of some past inhabitant ; others 

 contain portions of this Cliona sponge, living or dead ; others 

 again contain little bivalve shells that just fit the aperture, 

 whilst yet another set exhibit clean walls that may not have 

 had any animal inmate. Much controversy has raged over 

 the question whether these excavations have been made by 

 the sponge, or by some boring worm, and there have not been 

 wanting as advocates of either view men whose authority on 

 sponge matters is unquestioned. Where such doctors differ 

 how shall humble observers venture to give a verdict ? For 

 my part, I cannot give my support to the contention that the 

 sponge has bored the clean holes, hollows, and tubes that I 



