546 



SPONGES. 



grades, and uses names expressing the locality, texture, etc. The softest and finest 

 is the Turkey cup-sponge, which usually forms deep or shallow cups. The whole 

 outer surface of the dense horny network is covered with minute 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 some- 

 what closely resembles. The microscope shows the cause of the denseness to lie in 

 the thickness of the fibres composing the skeleton-network. 



The common bath-sponge, or horse-sponge (Hippospongia), 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 



SECTION OF COMMON BATH-SPONGE. 



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 lamella?, 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 "vesti- 

 bules " to the true pores, which can be seen on the walls. The pores corresponding 

 with those on the outer surface of a toilet-sponge may be deep in the interior of 

 a bath - sponge. The elephant's ear-sponge from the Adriatic is a variety of 

 Euspongia officinalis. It forms a huge lappet, the edges of which may unite to 

 form a funnel-shaped cup two or three feet in height ; the pores are on the outer 

 side, and the oscules in groups on the inner. Cut up into flaps a few inches 

 square, these sponges are useful for house-cleaning, etc. 



Many of the commoner kinds of sponges, termed hard-head, reef, etc., come 

 from the West Indies, and are included under E. zimocca. The bath-sponge 

 is less durable and more easily lacerated than the toilet-sponge, and has more 

 foreign particles in the fibres. In their natural condition toilet- and bath-sponges 

 look very different from the sponges in daily use. On seeing sponges in their 

 natural state, one wonders how it was discovered that they formed skeletons 

 possessing such useful qualities. A sponge living at the bottom of the sea appears 



