NORTH AMERICAN PORIFER^. PART II. 487 



of the North Pacific, ( Memou'es de I'Acad. Imp. de St. Petersburg, Vol. 75, No. 3.) 

 It would seem, therefore, that the finer skeletons of the Keratosa, those of the genus Spon- 

 gia, were only to be sought in the intermediate zone, where the watei^ are of equable and 

 high temperature. Again, in examining the species of this genus with relation to each 

 other, it becomes equally evident that they are finest and most numerous in archipela- 

 gos, or off' coasts which are bordered by large numl^ers of islands, or long reefs, or in 

 sheltered seas. I am informed Ijy Mr. Gurdon Saltonstall that the sponges near Nassau 

 lie on reefs very much exposed to the action of the waves, often thirty miles from land, 

 and always in currents, sometimes running three or four knots an hour. Such currents 

 are visual wherever groups of islands confine the tide water within certain definite chan- 

 nels, and they have also the effect of concentrating the floating food in the channels, or 

 wherever tides meet. Both of these conditions are essential to successful sponge growth, 

 namely, a continuous renewal of aerated water and a plentiful supply of food, and are 

 probaljly partly the cause of their abundance in such places. This entirely agrees with 

 my own observations upon many species on our own coast of Chalininas and Halichon- 

 drida. Constant reference to j^hysical influences is also noticeable in the map pre- 

 pared by Von Eckhel, and in the method of classification adopted by him. The mar- 

 ketable qualities are described as " sorts," and the different " sorts " designated by letters 

 as " sort A," " sort B," and so on. These sorts he has found it most convenient 

 to arrange according to localities, and thus imder some "sorts" we have all the three 

 species represented ; all, however, from the same place, and all having some local pecu- 

 liarity which makes them either of superior or inferior quality. The author also fre- 

 quently refers to the slimy character of the bottom as a reason for inferiority, or dark color. 

 On our side of the Atlantic this is also shown by the great difference in point of color 

 and fineness between the Nassau and Key West sponges. The former are lighter colored, 

 finer, moi-e elastic and more durable than the same species at Key West, where the color is 

 so dark that it designates at once the locality from which the specimen came. Again, the 

 shallow water sponges are coarser than the deep water forms. This is probably due, in part, 

 as in other species, to the quantity of sediment, which is of course less in deep than in 

 shallow water, as, for example, at Key West in the winter time. I am informed, in this 

 connection, by Mr. Saltonstall, who made inquiries for me among the spongers, that no fine 

 qualities of any sponges are found within the limits of the milky water, but all the finer 

 qualities of the marketable kinds in the deepest water in Avhich the species occur, excejDt, 

 perhaps, in the case of the Eeef sponge. Glove, Eeef and Hard-head, are fished in shallow 

 waters, greatest depth two fiithoms, and the other, and generally finer marketable varieties, 

 from two to five fathonis. This fiict also explains, in a measure, but not wholly, the 

 greater coarseness of our own sponges as compared with the European. For though it 

 may be assumed from the examination of the skeletons that Mediterranean sponges are 

 much less exposed to turljid waters, and though it may be shown by the microscope that the 

 primary fibres contain less debris, this does not wholly explain their greater fineness and 

 elasticity. I think that we may attribute this either wholly or partly to peculiar climatic 

 conditions. 



The Mediterranean Sea is divided by observers into two great basins, the Western and 

 the Eastern. Dr. Carpenter's recorded soundings on H. M. S. Porcupine and Shearwater ^ 



1 Pi'oe. Royal Society. Vol. XX, p. 578, 1872. 



