56 GLIMPSES OF NATURE. 



permeate the sponge-substance, and microscopic exa- 

 mination has told us a great deal about their nature. 



For, whether found in the canals of the sponge 

 themselves, or embedded in the sponge-substance, the 

 living sponge-particles are represented each by a semi- 

 independent mass of protoplasm. So that the first 

 view I would have you take of the sponge as a living 

 mass, is, that it is a colony and not a single unit. It 

 is composed, in other words, of aggregated masses of 

 living particles, which bud out one from the other, and 

 manufacture the supporting skeleton we know as " the 

 sponge of commerce " itself. Under the microscope, 

 these living sponge-units appear in various guises and 

 shapes. Some of them are formless, and, as to shape, 

 ever-altering masses, resembling that familiar animal- 

 cule of our pools we know as the Amoeba. These 

 members of the sponge-colony form the bulk of the 

 population. They are embedded in the sponge sub- 

 stance ; they wander about through the meshes of the 

 sponge ; they seize food and flourish and grow ; and 

 they probably also give origin to the "eggs" from 

 which new sponges are in due course produced. 



More characteristic, however, are certain units of 

 this living sponge-colony which live in the lining 

 membrane of the canals. In point of fact, a sponge 

 is a kind of Venice, a certain proportion of whose 

 inhabitants, like those of the famous Queen of the 

 Adriatic herself, live on the banks of the waterways. 

 Just as in Venice we find the provisions for the 

 denizens of the city brought to the inhabitants by 

 the canals, so from the water, which, as we shall see, is 

 perpetually circulating through a sponge, the members 

 of the sponge-colony receive their food. 



Look, again, at the sponge-fragment which lies before 



