DISTRIBUTION OF SPONGES. 845 



" Australia affords a few forms, and I have heard, though I cannot substantiate the fact, of 

 some species on the Atlantic coast of Brazil. Bermuda also has a few of the commercial kinds, 

 which, according to Mr. Goode's report, and the suite of specimens forwarded, are much coarser 

 than the Key West, darker in color, and, in fact, just about intermediate between these and those 

 of Australia. They are occasionally found in the stores, but, as a rule, are used only by the 

 nshennen themselves, about their boats, the Bahama Sponges being preferred for domestic 

 purposes by the inhabitants. 



"The true Spon flier- are all 'shallow-water forms. In the Mediterranean, according to Eckhel, 

 they are not found below thirty fathoms, and in our owii seas about the same, probably, though 

 not fished to greater than five fathoms. The greater part of the fishery is accomplished between 

 the depths of three and twenty feet, according to the report of Dr. Palmer, from whom these 

 remarks are principally derived. The commercial grades coincide very closely here and in 

 Europe, but it is quite easy to show that each of them may be considered a distinct species, if one 

 has an inclination to multiply in this direction. The three grades [of American Sponges], Glove 

 Sponge (Spongia officinalis), subspecies tubulifera, Wool Sponge (Spongia equina), subspecies gos- 

 s;/iiina, and Yellow and Hard Head, both tinder the name of (Spongia agaricina}, subspecies cor- 

 losia, correspond with remarkable accuracy to the three principal grades of commercial Sponges 

 in Europe. These are the Bath Sponge, Spongia officinalis, the Horse Sponge, Spongia equina. and 

 the Zimocca Sponge, Spongia agaricina. This result, in which three species appear on both sides 

 of the Atlantic, as representing alone the marketable qualities of the genus Spongia, becomes 

 of double interest when these varieties, or local species, as they might be called, are compared 

 with one another. It is then found that the aspect of the surface is closely similar in each 

 of the three; that subspecies tubulifera represents Spongia officinalis, subspecies gossypina offsets 

 Spongia equina in the same way, and, lastly, subspecies corlosia has the same relation to Spongia 

 agaricina. 



" The whole group of Keratosa is confined to seas in which the differences observable 

 between the winter and summer isotherms are not excessive. None are found north of Cape 

 Hatteras and the island of Bermuda, and doubtless a similar limit occurs to the southward of 

 the equator. 



"The finer skeletons of the Keratosa, those of the genus Spongia, are only to be sought in 

 the intermediate zone, where the waters 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 archipelagoes or off coasts which are bordered by large numbers of 

 islands or long reefs, or in sheltered seas. 



"The Sponges near Nassau lie on reefs very much exposed to the action of the waves, often 

 thirty miles from laud, and always in currents, sometimes running three or^four miles an hour. 

 Such currents are usual wherever groups of islands confine the tide water within certain definite 

 channels, 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 probably partially 

 the cause of their abundance in such places. 



"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 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 which the species occur, except perhaps in the 



