HORNY SPONGES 3521 



in the main fibres. The large purple fan-shaped lanthella from North Australia be- 

 longs to this group; also Lufforia archeri (Neptune's trumpet) from Yucatan, form- 

 ing a magnificent cornucopia, five feet in length. Darwinella possesses peculiar 

 horny spicules. 



The sponges commonly seen in shops may be arranged under three 



Bath species, all of which occur both in the Mediterranean and West Indies, 



Sponges namely, Euspongia offidnalis, variety mollissima, the fine turkey or 



toilet sponge; E. zimocca, the hard flat disc-shaped sponge; and Hip- 



pospongia equina, the common bath sponge or horse sponge. Under these species 



are included a large number of ' ' varieties ' ' and ' ' grades, ' ' classified according to 



form, quality of texture, color, locality, etc. The sponge merchant can define the 



exact locality whence a specimen came, by observing the presence of characteristics 



which the naturalist would not regard as specific. The merchant classifies his 



material into grades, and uses names expressing the locality, texture, etc. The 



softest and finest is the Turkey cup sponge, which usually forms deep or shallow 7 



cups. The whole outer surface of the dense horny network is covered with minute 



SECTION OP COMMON BATH SPONGE. 



holes, which correspond to the groups of in -current pores; in the cavity of the cup 

 are a few large holes about three-eighths of an inch in width, distributed irregularly 

 or with a tendency to a radiate arrangement. The large holes are the oscules or 

 out-current apertures. The second species is the zimocca or hard sponge, typically 

 forming rounded discs, convex below and flat at the top. The pores are arranged on 

 the outer side or margin, and a number of oscules cover the flat upper surface. 

 The texture is denser and less resilient than that of the toilet sponge, which it 

 somewhat closely resembles. The microscope shows the cause of the dense- 

 ness to lie in the thickness of the fibres composing the skeleton network. 



The common bath sponge or horse sponge (Hippospongia) t presents such wide 

 differences from the first two forms, that the naturalist places it in a different genus. 

 The holes on the surface of the loaf-shaped hemispherical mass do not correspond 

 to those in a toilet sponge. The in-current and out-current orifices are in the walls 

 of the wide canals which permeate the whole sponge body, so that the bath sponge 

 is really composed of much folded layers, or lamellae, with the canal system in the 

 thin walls of the lamellae. The large holes on the surface are " pseudoscules," and 

 the tortuous passages into which they open are "vestibules" to the true pores, 



