1 68 The Commercial Products of the Sea. 



a modification of the cup-shape, is absent. Spongia equina 

 exhibits similar degrees of variation in the texture of the 

 surface and the form. There are no proper cup-shaped 

 specimens among the American varieties of sub-species 

 gossypina, but in place of these the fistular form. These 

 occur generally associated in clumps, more or less densely 

 filled up into heads, and solid, but sometimes the tubes are 

 almost isolated. The younger specimens of this species 

 have a very loose and open texture, due to the approxima- 

 tion and large size of the openings, and to a less degree 

 this is also to be remarked in the gerbis sponge. The 

 former approximate in aspect to the coarser qualities of 

 the American species, and so also does the latter, which 

 has very nearly the same colour and aspect as the dark- 

 coloured Key West specimens, but it is not so coarse or 

 dark. It seems, then, that there are three sub-species of 

 commercial value in the Mediterranean, which find their 

 way into the New York and European markets. The 

 coarsest varieties of the European sponges are finer, firmer, 

 and more elastic than the finest of the corresponding 

 American sub-species. This is directly traceable to the 

 larger amount of foreign matter included in the primary 

 threads, the looser mesh of the tissue ; the fibres are also 

 comparatively coarser and the large cloacal channels more 

 numerous throughout the mass. 



Thus the different varieties of sub-species gossypina 

 differ in an exactly similar way from each other, and from 

 the third form, sub-species cerebrifoj'inis ; they differ in 

 texture, in surface, and also in habitat, the finer kinds, as 

 stated previously, being found in the deeper water, equally 

 removed from excessive heat and excessive sediment. 

 These three sub-species run together by means of specimens 

 of the coarser varieties, which cannot be distinguished 



