166 T>r Grant withe Structure 



west Passage, which, from the known activity of that body, may 

 l)e agreed too, and thus, in all probability, we shall hear of the 

 American flag traversing the Polar Sea, and doubling Icy Cape. 

 The Americans, by this achievement, would secure to them- 

 selves and deservedly, a splendid name in the annals of geogra- 

 phical discovery, — a name that ought to be ours, and which 

 would add another and enduring laurel to the wreath of glory 

 which surrounds the maritime honour of this nation. 



Remarhs on the Structure of some Calcareous Sponges. J5y 

 Robert E. Grant, M. D., F.R.S.E., F. L. S., M.W.S., 

 &c. Communicated by the Author. 



JL HE Spong'm compressa Fabr. Gmel. Latnouroux, (S./b- 

 liacea, Montagu), affords a good example of a species in which 

 the axis is composed entirely of calcareous spicula. This is a 

 small white tubular compressed species, generally about an inch 

 in length ; it hangs from the under surface of rocks by a thick 

 short peduncle ; it is entirely hollow, and opens by one or more 

 marginal apertures at its pendent extremity ; its parietes are of 

 equal thickness throughout, nearly as thin as writing paper, and 

 every where pierced with minute openings, which are visible to 

 the naked eye on the external and internal surface, and its cur- 

 rents are distinctly visible, both those passing in through the 

 pores, and those issuing from the large pendent orifices. It is 

 a hardy species, growing in very exposed situations, and in cold 

 climates. Fabricius observed it on the coast of Greenland, Pro- 

 fessor Jameson and Dr Fleming on the shores of the Shetland 

 Islands, Montagu on the coast of Devonshire, and I have found 

 it very abundant in the Frith of Forth. They hang like small 

 white leaves from the surface of rocks, at low-water mark, 

 being always in a collapsed state, and their opposite sides in 

 contact during the retreat of the tide ; but, when suspended for 

 a short time in pure sea water, their parietes separate, and they 

 become like small distended bags pouring forth a continued and 

 obvious current. The pores pass through their parietes in a 

 direction a little oblique, from below upwards, and the margins 



