764 



The Living Animals of the World 



CHAPTER VII. 



SPONGES AND ANIMALCULES. 



THE SroNGES are regarded as a group standing on the borderland 

 between the Polyps and the lowly organisms which follow. 

 The familiar Bath- and Toilet-sponges of commerce represent 

 but an insignificant fraction in comparison with the many hundred 

 species which find no place in the world's market. Toilet-sponges 

 owe their intrinsic value to the relative fineness and elasticity of 

 their component fibrous skeletons. In these particular species the 

 skeleton is composed of a substance akin to horn. In other sjionges 

 the skeleton may consist of horny fibres mixed with flinty sjoicules, 

 or it may be of flint only, or of spicules of carbonate of lime. 

 Finally, there are sponges which possess no internally supjwrting 

 skeleton, fibrous or spicular, and whose substance is consequently 

 little more than gelatinous. All these numerous forms, however, 

 agree with one another in the identity of their most essential vital 

 elements. In the living sponge the skeleton, fibrous or otherwise, 

 is embedded within a gelatinous matrix by whose component cells 

 it is excreted. Externally the sponge-body is perforated over the 

 greater portion of its extent 



Fliotobii ir. Sai-ilh-Knit, F.Z S., 

 MilJ'ord-ofl-^ia. 



FEILLED SPOXGE. 



A species not inf 1 ecjuently d rcdged 

 np by the pe;ii]-shell fisher-s iu Sharks 

 Bay, Western Australia. 



by minute holes or pores, 

 while one or more holes of 

 relatively large size occupy 

 (he summit of the sponge, 

 or are scattered here and 

 there among the numerous 

 smaller pores. The smaller 

 pores represent in current aper- 

 tures, and lead to chambers 

 within the sponge's substance 

 lined .by cells. Each of these 

 is provided with a long whip- 

 like appendage, with a trans- 

 parent wineglass-shaped cup 

 or collar, which is a beautifully constructed food-trap. 

 The lashings of the whips of the collar-cells cause 

 currents of water bearing nutrient particles to flow in 

 at all the smaller pores. Arriving at the chambers, 

 tliese particles are caught by the outstretched collar-tra])S 

 and absorbed into the cell's substance. The water, 

 together with rejected and waste materials given off bv 

 the sponge-body, is carried forward, and jiasses out at the 

 larger orifices or A-ents. 



Among the more remarkable si:)onges may be men- 

 tioned the Neptuke's-CUP Sponge, like a huge chalice 

 3 or 4 feet high, indigenous to the South Seas; the 

 wonderful cornucopia- shaped Lace-Sfonge, consisting of 

 a lace-like reticulation of flinty fibres ; and its near 

 ally tlie Glas.s-rope Sponge, forming a cup- or l)ird's- 

 nest-shaped body, sui)ported on a long cylindrical stalk 



Photo bi/ W. SavUU-Ki,i(, F.Z ^., Mi(i«r,l-o,i-Sca. 



RETICULATED SPOXGE. 



The skeleton of this s^wnse is composed of fine horny 

 fibies resembling those of ordinary comn-.ercial sponges. 



