138 THE IMPERFECTION OF 



definite temperature, glaciers scoring the rocks, icebergs 

 transporting boulders, rains and rivers slowly washing 

 down the hills, and waves corroding the cliffs on the 

 sea-shore. We have evidence also that life in many 

 forms abounded. Those forms, though seldom trans- 

 mitted to creatures of the present day with anything 

 approaching an exact likeness, can yet be classified 

 under the same general names with the most modern 

 forms of life. Now sponges are forms of an extremely 

 simple organization. The silicious spicules are well 

 adapted for the wear and tear of a fossil existence. 

 In the greensand and the chalk they are actually found 

 in extraordinary abundance. It would be inconvenient 

 upon any theory to have to suppose these very simple 

 structures introduced into the world for the first time 

 quite late in the series of living organisms, and after 

 beings much more complicated and higher in the scale 

 of existence, unless, indeed, we suppose that about the 

 time of the Great Oolite the evolution of man was first 

 thought of, and the sponge accordingly prepared for him 

 to wash his face with. But even if the bath and the 

 basin be admitted as the final causes of sponge-existence, 

 the conception of it must be carried back, as we have 

 seen, to the Silurian period ; while, according to Mr. 

 Parfitt, the immense interval of Lias and Trias, Per- 

 mian, Carboniferous, and Devonian remains black and 

 spongeless, as though it were the appropriate era of 

 the great unwashed. But if the Darwinian theory be a 

 true one, sponge-life having begun in the Silurian 

 period, and being in existence now, must have been 



