114 THE HARMONIES OF NATURE. 



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 the larger apertures or oscula. Thus by a still 

 mysterious agency (for the presence of cilia has as yet been 

 detected but in one genus of full-grown marine sponges), a 

 constant circulation is kept up, 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 vomiting 

 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 animal kingdom long arrested my atten- 

 tion, 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 diminish 

 in the slightest degree the rapidity of its course.' 



Subsequent observations have proved that the living sponge 

 has the power of opening and closing at pleasure its oscula, 

 which are capable of acting independently of each other, 

 thus fully establishing the animal nature of these simple organ- 

 isations, in whom latterly even traces of sensibility have been 

 detected, such as one would hardly expect to meet with in a 

 sponge. For these creatures, as we are entitled to call them, are 

 able to protrude from their oscula the gelatinous membrane which 

 clothes their channels, and on touching these protruded parts 

 with a needle, they were seen by Mr. Gosse to shrink immedi- 

 ately , a proof that the sponge, however low it may rank in the 

 animal world, is yet far from being so totally inert or lifeless 

 as was formerly imagined. 



The propagation of the sponges is provided for in a no less 

 wonderful manner than their respiration and nourishment. 

 Their young eggs or sporules germinate on the sides of the 



