846 -. IfATURAL HISTORY OP AQUATIC ANIMALS. 



case of the Reef Sponge. Glove, Reef, and Hard Pead are fished in shallow waters, greatest- 

 depth two fathoms, and the other, and generally finer marketable varieties, in from two to five- 

 fathoms. This fact also explains in a measure, but not wholly, the greater coarseness of oqr own 

 Sponges as compared with the European. For though it may be assumed, from the examination 

 of the skeletons, that Mediterranean Sponges ai'e ifiuch less exposed to turbid waters, and though 

 it may be shown by the microscope that the primary fibers contain less dSbris, this does not 

 wholly explain theiu greater fineness and elasticity. I think that we may attribute this either 

 wholly or partly to peculiar climatic conditions. 



"The coral reefs afford good holding ground for the bases of the colonies, and protection 

 from the excessive surf of ocean shores, while they grow in water the remarkable clearness of 

 which to a considerable depth is constant subject of remark. These are undoubtedly favorable 

 conditions, as they are common also to the Mediterranean waters. The gTcat quantity of cal- 

 careous sediment, however, which is churned by the waVcs in the winter, on the borders of a, 

 coral reef, is not present in the Mediterranean; and the average temperature also, which is very 

 much higher than that under which the finest Sponge skeletons are produced in the Mediter- 

 ranean, cannot be considered as favorable. These last, then, are probably the direct cause 6f the 

 inferiority of the skeleton of the commercial varieties found in this association [i. e., many of the 

 American varieties]. * 



"The coarsest quality of all the Mediterranean Sponges, the Gherbis sort and other coarse 

 sorts, grow in localities along the coast, where they are most subject to the action of suspended 

 matter in the water; but all of these are, however, on account of the clearness and medium 

 temperature of the Mediterranean waters, as compared with those of other seas, of much finer 

 quality. 



"The coarser kinds of the same variety grow nearest the shore, and the finer kinds in deeper 

 water, and also, according to Nassau spongers, are more apt to occur on marly ground, where the 

 sediment is finer than upon other kinds of bottom. The openness which usually accompanies 

 and appears to correlate with coarseness of the fiber must be considered as one of the elements 

 of inferiority, which invariably accompanies a skeleton having a loose microscopical texture or 

 mesh, and harsh or inelastic or easily torn fibers, but is also, though rarely, found in skeletons of 

 very fine quality, especially at an early age. Thus it may be said that it is undoubtedly a 

 common characteristic of all the inferior qualities of Mediterranean, and of all the , Caribbean 

 commercial Sponges without exception, which, though they may have very fine or very coarse or 

 inelastic fibers, are always permeated in the interior and have the surface also cut up by larger 

 and more numerous canals than the corresponding Mediterranean species." 



238. THE GENUS SPONGIA AND THE AMERICAN COMMERCIAL SPONGES. 



The skeleton of this genus, according to Professor Hyatt, is composed of solid, elastic fibers,, 

 the primary ones, those having their origin in the external integuments, being usually, though 

 not invariably, morte or less radiatory in their arrangements; but the secondary or connecting 

 fibers are excessively irregular, and generally very closely intertwined. The primary fibers are 

 particularly noticeable on the inner side of the walls of the large or excurrent openings. The 

 skeleton exhibits a very rough surface, due to the development of large projecting masses of the 

 secondary or connecting fibers, which are separated by horizontal channels of greater or less 

 depth. The primary fibers protrude above the surface of the cushions or ridges thus formed 

 carrying with them more or less of the secondary fiber, and forming a series of superficial tufts, 

 . giving the skeleton a peculiarly hirsute aspect. The pores through which the water enters the. 



