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Cincinnati Society of Natural History. 



fibrous skeleton is almost entirely destitute of spicules, a circumstance to 

 which it owes the flexibility aud softness that render it so useful to man ; 

 while they predominate in the Halichondria, and sometimes even as in the 

 Grantia completely supersede the horny fabric 



On examining a sponge, the holes with which the substance is every- 

 where pierced may be seen to be of two kinds : one of larger size than the 

 rest, few in number and opening into wide channels and tunnels which 

 pierce the sponge through its center ; the other minute, extremely numer- 

 ous, covering the wide surface and communicating with the innumerable 

 branching passages which make up the body of the skeleton. Through 

 the smaller openings or pores, the circumambient water freely enters the 

 body of the sponge, passes through the smaller canals, and ultimately 

 reaching the larger set of vessels, is evolved through he larger aperturest 

 or 'Oscula. Thus by a still mysterious agency (for the presence of Cilia 

 has as yet been detected in but one genus of full-grown marine sponges), 

 a constant circulation is kept ap, providing the sponge with nourishing 

 particles and oxygen and enabling its system of channels to perform the 

 functions both of an alimentary tube and a respiratory apparatus. 



Dr. Grant describes in glowing terms his first discovery of this highly 

 interesting phenomenon. ;> Having put a small branch of sponge with some 

 sea water, into a watch glass in order to* examine it with the microscope 

 and bringing one of the apertures on the side of the sponge fully into 

 view, I beheld for the first time the spectacle of this living fountain, vom- 

 iting forth from a circular cavity, an impetuous torrent of liquid matter, 

 and hurling along in rapid succession opaque masses, which it strewed 

 everywhere around. The beauty and novelty of such a scene in the Ani- 

 mal Kingdom long arrested my attention, but after twenty -five minutes of 

 constant observation, I was obliged to withdraw my eye from fatigue, 

 without having seen the torrent for one instant change its direction or di- 

 minish in the slightest degree the rapidity of its course. I continued to 

 watch the same orifice at short intervals for five hours, sometimes observ- 

 ing it for a quarter of an hour at a time; but still the stream rolled on 

 with a constant and equal velocity.'' 



The innumerable canals by which the sponge is traversed — according to 

 Milne- Edwards — are at once its digestive organs and breathing pores. The 

 vibratile cilia are necessary to the renewed aeration of the water required 

 as a respiratory fluid in the interior canals of the sponge. The currents 

 in these channels have one constant direction. The water penetrates the 

 sponge by the numerous orifices of minute dimensions and irregular dispo- 

 sition it traverses channels in the body of the mass and finally makes its 



