S4S Dr Grant's Ohservatimis cm the 



straight, thick, short, cyhndrical, pointed rather obtusely and 

 suddenly at one extremity, and rounded, but not swelled at the 

 other ; they are of various thickness, but of one form and length, 

 they are fused by the aid of potassa, resist heat and acids, scratch 

 glass, &c. In specimens of the panicea which I brought this 

 summer from the Island of Staffa, the spicula have the same 

 characters as in those which abound in the Frith of Forth ; 

 and the same form of spiculum is met with in the Spmigia pa^ 

 rasitica of Montagu. In the large Spongia patera of the In- 

 dian seas, many specimens of which have been lately brought 

 to Europe, and six of which are preserved in the Museum of 

 our University, measuring from two to four feet in height, the 

 spicula are silicious, long, thick, cylindrical, slightly curved, 

 pointed at one end, and in place of being simply rounded or 

 truncated at the opposite end, like those of the panicea^ we ob- 

 serve them all headed like pins with a distinct sphere or round 

 bead on one extremity, which has twice the diameter of the rest 

 of the spiculum. I have elsewhere shown that this one-pointed, 

 curved, headed spiculum, occurs in the Climia celata^ a zoophyte 

 possessing polypi and very distinct irritability ^ (see p. 80), so 

 that it would be highly interesting to examine whether the cup- 

 like sponges, found so abundantly near Sincapore, do not ma- 

 nifest likewise some signs of contractility in the living state. 



A third distinct form of spiculum, met with in siUcious spon- 

 ges, is where one of the sharp points is lost, and the whole 

 spiculum appears to be composed of a series of round transpa- 

 rent beads, diminishing in size from one extremity to the other. 

 This remarkable form I have yet observed only in one species, 

 a thick, branched, tubular, yellowish brown, rough, wiry sponge 

 from the Indian seas, from the zoological collection of a zealous 

 young naturalist Mr John Coldstream of Leith. The bran- 

 ches are about IJ inch in diameter, cylindrical, dichotomous, 

 tubular, of a hard and very tough texture, and marked on 

 the outside with distinct open round pores, which pass direct- 

 ly through the thick parietes, and open into the internal tu- 

 bular cavity by somewhat larger orifices. These tubular branch- 

 es are of course open at their free extremities for the exit 

 of the currents ; their openings are cylindrical, wide, and 

 with rounded margins. The remarkable notched spicula are 

 seen with the naked eye projecting on every side perpen- 



