POBIFERA, OR SPONGE TRIBE. 559 



rather be assigned to the Vegetable Kingdom. Perhaps the 

 strongest argument for their Animal nature, is to be found in the 

 resemblance of their structure to a part of that, which constitutes 

 beings whose animal character is undoubted. The group of 

 Alcyonia ( 1087) consists of Sponges with Polype-mouths; and 

 in the growth of these structures, the spongy mass is first formed, 

 the polypes not appearing until a subsequent period. The 

 substance commonly known as Sponge is in reality but the frame- 

 work or skeleton of the being in its living state. When growing 

 beneath the waters it inhabits, this framework is covered by a 

 living flesh, which not only envelopes its exterior, but lines all 

 the canals that ramify through its substance. This enveloping 

 flesh is so extremely soft, as to drain away when the mass 

 is removed from the water, like the white of an egg, or the 

 vitreous humour of the eye ; hence its existence was for a long 

 time overlooked, and the mode in which the harder texture 

 grows was not at all understood. It is principally to the obser- 

 vations of Dr. Grant (which have been confirmed by other 

 naturalists), that we owe the elucidation of the real character of 

 the spongy structure, and of its concern in the actions performed 

 in the living state. 



1139. When we examine the exterior of a piece of common 

 Sponge, we observe that it is covered with minute orifices or 

 pores (whence the name which has been given to the class), 

 thickly set together ; and that larger openings are disposed at 

 intervals amongst these. If these larger orifices, or vents, be 

 traced into the substance, it will appear that they are the 

 mouths of canals or vessels which ramify through it ; these have 

 definite walls formed by the firm tissue of the sponge, but per- 

 forated with a large number of orifices, connecting them with 

 the spaces that lie between their net-work of branches. The 

 pores, on the other hand, open into a less regular arrangement of 

 small tubes and cells, of which the spongy mass is principally 

 composed. These spaces are produced by the interlacement of 

 the fibres that form the solid framework ; they communicate 

 with one another throughout the mass ; and the canals seem to 

 take their origin from the midst of them, arising by small tubes 



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