1 6 SPONGES. 



Sponges in fact, few things could be pointed out more unlike 

 each other. Infinitely diversified in their shape, the sponges, as 

 we all know, are distributed along the shores of every climate : 

 some overspread the surface of the rocks like living carpets, 

 others expand in fan-like growths of softest texture ; some are 

 cylindrical in shape, while others emulate the forms of branching 

 shrubs ; others, again, are moulded into cups and giant goblets, 

 many festoon the walls of rocky caverns, or depend, like living 



FIG. 7. -Si ONGES. 



stalactites, from wave-worn roofs. Examined with a microscope, 

 however, a living sponge is found to differ but little from the 

 organisms we have just been contemplating. No matter what 

 its form, the living portion of a sponge consists of a soft slime 

 that coats each fibre of its structure, and this soft slime, when 

 highly magnified, resolves itself entirely into particles so like the 

 Amoeba in their characters and attributes, that they are evidently 

 of the same nature, the main distinction being that, whereas in 

 the case of the Foraminifera, they secrete a calcareous shell, the 

 sponges construct a common framework, over which the living 

 film is spread. This framework varies in its composition in dif- 

 ferent kinds of sponge. Sometimes it is made up of tubes of horn, 



