SPONGE-FISHING. 



547 



as a shining, blackish, fleshy lump, which cuts like raw meat, no trace of the 

 horny network being 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 contracting. 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 good 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 greyish, some 

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

 acean, others, again, being empty. The skin-pores open into sub- 

 dermal 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 yellowish and translucent, and built up of concentric layers 

 surrounding 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 settle down by becoming fixed at one end, and 

 develop into sponges. 



In addition to sexual reproduction, there is also vegetative 



propagation. This characteristic has been made use of for cultivating sponges by 

 cuttings. 



SPONGE-FISHING. 



Sponges are found in depths ranging from two to one hundred fathoms, and 

 the methods of collecting depend both on depth and locality. Off Dalmatia the 

 primitive method of harpooning is still employed. Two men go out in a small 

 boat ; one rows, the other leans over the edge holding a long fork. If the water 

 ripples, the rower throws in a half circle in front of him a few pebbles dipped in 

 oil. The Greeks employ a submarine spyglass, which simply consists of a pane 

 of glass let into the bottom of a tube or bucket. By this means they do away with 

 the effect of the surface ripples. In the Levant in depths of five to fifty fathoms 

 divers are employed, either naked or provided with a diving-dress. In the former 



Ascetta primordialis. 

 After Haeckel. 



