62 ON THE PROPAGATION 



stances in former ages. And yet, all that we can make out 

 as to the number of the great animals of the past world, 

 dwindles into nothing before the masses of diminutive crea- 

 tures which have been preserved to us. The whole of those 

 elevated ridges, partly still subsisting, partly destroyed by 

 later floods, for instance, from Rugen to the Danish islands, 

 the white chalk rocks, which gave England the name of 

 Albion and stretch through France to the south of Spain, 

 the whole of the chalk mountains of Greece to which, among 

 others, Crete owes its name, consist, according to Ehren- 

 berg's researches, of the shells of minute animals, partly 

 destroyed, partly well preserved. When we turn to these, 

 the smallest creatures which Nature exhibits, existences 

 which make up by the number of individuals what the 

 individuals want in size, animalcules which are mostly so 

 small as to be invisible to the naked eye, yet fulfil an 

 important purpose in the universal life of Nature, the 

 imagination is wholly unable to express the quantity in 

 abstract numbers. Ehrenberg's discovery of fossil Infusoria 

 has deservedly attracted great attention, for every picture 

 here fails to enable us to grasp the conception of such 

 numbers. In one cubic inch of the tripoli (polir-schiefer) 

 of Bilin, there are forty-one thousand millions of animals, 

 and the whole deposit extends over from thirty to forty 

 square miles, with a varying thickness of from two to 

 fifteen feet. 



Making a more special examination of the animal world 

 in general, we find two great divisions determined by the 

 nature of their food, whether vegetable or animal. The 

 latter contains by far the smallest number of species, and 

 the particular species appear in small numbers. The 

 vegetable feeders, on the contrary, are innumerable ; if 

 we may adopt the excessive estimates of recent works, we 



