CONCLUSION. 181 



all hidden beneath that very visible exterior ; and 

 in this sense there is no mistake in classing our 

 Sponge life with the invisible. Still, this illus- 

 tration, so far, is only an approximation to our 

 idea. To make the matter plainer, let us say 

 that although we are daily looking on natural 

 objects, or rather on living forms, as bird, beast, 

 flower, and tree, yet that in reality we see only 

 the external forms, underneath which the real life 

 is hidden. We perceive the organised structure, 

 but not the living matter the product, but not 

 the agent. 



Cutting, or tearing open the Sponge, we can, as 

 previously described, by the aid of the microscope, 

 and that alone, see the otherwise invisible agents, or 

 the living forces, the nearest approach to actual 

 living matter, which in its essential purity is with- 

 out any structure or organisation whatever. This 

 Amoeboid matter, or protoplasm, is then the hidden 

 basis of life, animal and vegetable, the invisible 

 agent of all organisation. It is a singular fact 

 that this living matter cannot be analysed, for 

 the instant this is attempted its essential quality, 

 that which is its prime element, eludes our grasp : 



