NOKTH AMERICAN PORIFER^. PART II. 517 



Spongia equina Schm. 



Sjoongia equina Schm., Spongien d. Adr. Meeres, p. 23, pi. 2. 



This s2Decie.s more closely I'esembles our ordmary forms of West Indian sponges than 

 any other European species. The form may vary considerably, but is remarkably and 

 constantly solid in the specimens offered for sale, and semi-globular in form. The 

 color of the fibre externally, and the tufted surface, shows the same close approximation 

 to the corresponding American forms of the sub-species gossyj^'ma, as was noticed in the 

 preceding species. It has a similar oj^enness, being a net woi'k of large excurrent orifices 

 closely approxunated and fringed with prominent bundles of superficial fibres. These 

 characteristics are also particularly marked in the young, especially in those varieties 

 which grow laterally into flattened fonns. Compare for purposes of identification. Fig. 1 

 with Fig. 8, PL xvi. The first is a flat variety of a Mediterranean sponge, and the latter a 

 fragment cut out of the side of an aged specunen of sub-species fjossypina, of remarkably 

 fine texture. There is here evidently a fact of the same nature as that previously noticed 

 in the comparison of the Mediterranean sub-species of Spongia officinalis with the Amer- 

 ican sub-species ; the approximation in each case is made by means of the inferior qual- 

 ities, the aberrant forms. Or if the comparisons are made between the stage of growth 

 of any single colony of the American sub-species and the coarser kinds of the Mediterra- 

 nean sub-species, the closest approximation is obtained by comparing the old age of the 

 American sponge with the full grown of the European. This is due to the fact that the 

 American sub-species loses in old age the tufts, or prominent pencils of primary fibres 

 which are so numerous in the adult colonies. 



The Gherbis sponge (PL xvi, fig. 9), a " sort" which occurs between Tunis and Ceuta, 

 has a darker color and coarser fibre thfin the more eastern varieties. This color and the 

 aspect of the surface make them very similar to the American, especially the Key West 

 forms of sub-species gossypina, and this resemblance is rendered even more exact by the 

 structure of the superficial bundles of fibres, which are much broader and more loosely 

 connected than is usual in the Mediterranean sponges, giving the surface of some speci- 

 mens a precisely similar aspect. 



In the shojDs this sponge frequently goes by the name of the "Venetian Bath-sponge, 

 though in Europe the only name popularly employed seems to be that of Horse Sponge. 



Sub-species gossypina. 



The fibres are generally, but not invariably, somewhat coarser than those of hihulifera. 



1. Primary fibres single, widely separated, continuous below, projecting above, stouter 

 than those of tubuUfera. The meshes of the connecting fibre are also very broad, some- 

 times extending without interrujition from one primary fibre to another. 



2. Primary fibres in groups, Ijut not fasciculated. They converge towards the surfiice, 

 and project in several apparently single points. Meshes of the connecting fibre narrow 

 and long, or of equal dimensions, but never so large as in No. 1. 



3. One section of sub-species meandrina shows the primary fibres absolutely free of 

 debris, rising in single points above the surface, but not continuous ; they being soon lost 

 below the surface in the small, dense net work. 



MEMOIRS BOST. 600. NAT. HIST. TOL. U, 



