68 THE HISTORY OF CREATION,' 



now add some further general observations on tlieir 

 natural history. The great majority of all Protista 

 live in the sea, some swimming freely on the surface, 

 some creeping at the bottom, and others attached to 

 stones, shells, plants, etc. Many species of Protista also live 

 in fresh water, but only a very small number on dry land 

 (for example, Myxomycetes and some Protoplasta). Most 

 of them can be seen only through the microscope, except 

 when millions of individuals are found accumulated. Only 

 a few of them attain a diameter of some lines, or as much 

 as an inch. What they lack in size of body they make up 

 for by producing astonishing numbers of individuals, and 

 they very considerably influence in this way the economy of 

 nature. The imperishable remains of dead Protista, foi* 

 instance, the flinty shells of the Diatomese and Radiolaria, 

 and the calcareous shells of the Acyttaria, often form large 

 rock masses. 



In regard to their vital phenomena, especially those of 

 nutrition and propagation, some Protista are more allied to 

 plants, others more to animals. Both in their mode of 

 taking food and in the chemical changes of their living sub- 

 stance, they sometimes more resemble the lower animals, at 

 others the lower plants. Free locomotion is possessed by 

 many Protista, while others are without it ; but this does 

 not constitute a characteristic distinction, as we know of 

 undoubted animals which entirely lack free locomotion, and 

 of genuine plants which possess it. All Protista have 

 a soul — that is to say, are "animate " — as well as all animals 

 and all plants. The soul's activity in the Protista manifests 

 itself in their irritability, that is, in the movements and 

 other changes which take place in consequence of mechau- 



