3522 THE SPONGES 



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 gores 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 use- 

 ful qualities. A sponge living at the bottom of the sea appears as a shining, 

 blackish, fleshy lump, which cuts like raw meat, no trace of the horny network be- 

 ing visible. The discovery would probably result from finding cast up specimens 

 with the skin and flesh partly rotted away from the more durable skeleton. A 

 toilet sponge when alive is a blackish, cup-shaped fleshy mass, with its surface 

 covered with minute conical elevations. In the hollow of the cup are the oscules, 

 which appear smaller than in the skeleton, and are capable of dilating and contract- 

 ing. During life currents rush out of these holes. On the outer surface of the 

 sponge, by very careful inspection, sieve-like groups of pores will be seen in the 

 skin, between the conical elevations. 



When a living sponge is torn or cut, a great deal of glutinous substance flows 

 away. The dark skin covers a light yellow fleshy substance, in which the canals 

 leading to the oscules are conspicuous. The walls of the canals are grayish, some 

 being filled with mud, others containing a marine worm or crus- 

 tacean, others, again, being empty. The skin pores open into 

 subdermal spaces beneath, and from the floor of the latter canals 

 branch into the body substance. The smallest canals finally 

 open into minute pyriform flagellated chambers; and from each 

 of the latter there arises a rootlet of the out-current canal system. 

 What is commonly known as the sponge forms a supporting 

 network of fibres in the gelatinous ground substance, the horny 

 skeleton forming a kind of scaffolding. The fibres are yel- 

 lowish and translucent, and built up of concentric layers sur- 

 rounding a thin axial thread. Foreign particles, such as sand 

 grains, flinty spicules of other sponges, etc., are included in 

 the main fibres. Each growing fibre is surrounded by cylindrical 

 cells which secrete it. When a fresh batch of cells secretes 

 a new layer, foreign particles on the surface of the fibre 

 become included within the new coating. The embryos 

 are minute oval bodies, which swim by means of their cilia, 

 and lead an independent life for a day or two. They then 



Ascettaprimordialis. Settle down by becomin S fixed at one end > and develop into 

 (After Haeckel). Sponge" 



