and Functions of the Sponge. 341 
ter of an hour, while the torrent was in full activity, the spicula 
projecting from the margins of the orifice never moved. 
From these experiments, performed with every precaution, 
and frequently repeated during many months’ study of zoophytes 
upon the coast, I am persuaded that the sponges of the Frith 
of Forth above enumerated do not exhibit naturally a systole 
and diastole, or palpitation of the fecal orifices, nor can be forced 
to exhibit these motions by very powerful irritation. This is a 
sufficient reason for abandoning such a property as a general 
character of this immense genus of animals, even though species 
should hereafter be discovered in tropical seas, which actually 
exhibit such extraordinary and useless motions ; and these ex- 
periments likewise serve to shew, that there is no necessary con- 
nection between such motions and the currents, or other func- 
tions of this mysterious being. From the close resemblance in 
horny fibrous structure, which I observe in the dried sponges of 
distant seas, which I have been allowed to examine by the libe- 
rality of Professor Jameson, and from the outward form and 
appearance of those which I have seen growing on the shores of 
Italy and France, I am convinced that it is a property as little 
possessed by them as by the sponges of the Frith of Forth. 
Cavolini, indeed, both irritated and punctured, with sharp instru- 
ments, the surface of the large Spongia officinalis , while still 
growing on its native cliffs in the Gulf of Naples, and still under 
the surface of the sea, without producing the slightest change in 
the dimensions of its apertures ; and though his observations were 
published forty years ago, we find this singular property ascribed 
to the officinal sponge by the naturalists of the present day. 
When we look on the surface of a living sponge, and observe 
its numerous papillae projecting from the body, and all termi- 
nated by circular openings of different dimensions, from which 
currents of water are constantly pouring out, it is difficult to 
persuade ourselves that each orifice has a fixed diameter ; we 
naturally expect them to contract occasionally, as we are accus- 
tomed to see done by the similar openings of many molluscous 
animals, and the motions caused by the sponge in the mass of 
the water may somewhat confuse the vision, and thus assist the 
imagination. When a globule of air is advancing through an 
orifice under water, it has the effect of diminishing very much 
