107 
Functions of' the Sponge . 
the free entrance of water, through the minute pores on its sur- 
face, that these animals enjoy health or existence; and we shall 
find the arrangement, form and structure of these pores, beauti- 
fully calculated to prevent the entrance of all grosser particles 
into the interior of the canals. 
Mr Ellis was probably led to imagine that the currents passed 
to and fro through the same apertures, and thus to compare 
these openings to Polypi, by observing the irregularity of the 
feculent discharges, which do not come out in particles, and in 
a constant stream, but generally in flakes at intervals, in the 
species which he examined ; or he may have been deceived by 
the appearance of the whirlpools that are generally seen at the 
sides of the apertures when they are near the surface of the water. 
But it was of much importance in the physiology of the sponge, 
to determine precisely the nature and direction of these currents, 
because the power of sucking in and throwing out water by the 
same orifices, like Polypi, hitherto ascribed to this animal, ne- 
cessarily implied the existence of two other properties which it 
has long been supposed to possess, the power of contracting and 
dilating its apertures, and that of contracting or shaking its 
whole body when touched. 
( To be continued.) 
Art. X .— Sketch of the Geology of Sicily. By Charles Dau- 
beny, M. D. E. ft. S, Professor of Chemistry in the Univer- 
sity of Oxford *. With a Map, PI, IV. 
Xn submitting the following brief outline of the geology of Si- 
cily, I wish it to be understood that my principal objects are, 1st, 
To afford an explanation of the suite of specimens from that 
country, which I lately presented to the institution ; and, Qdly, 
To supply such hints with regard to the general bearings of the 
strata as may facilitate the inquiries of other travellers, who, with 
similar views to my own, may chance hereafter to visit that island. 
To fulfil the above objects, it seemed to me more advisable 
that the information I had collected should appear at once even in 
Read at the Bristol Philosophical Institution, April 14. 18?5. 
