INTRODUCTION 9 



resemblance to fungi. But they exhibit a curious 

 resemblance to the movements of Amoeba, a Proto- 

 zoan, in the streaming or creeping motion of the 

 Plasmodium. They also resemble Amoeba in mode 

 of nutrition. 



For this and other reasons a common kingdom 

 Protista has been suggested for the lower types of 

 plants and animals, viz. : Protophyta and Protozoa. 

 Professor Keeble, moreover, has shown by his re- 

 searches on Convoluta that certain organisms may 

 properly be called " plant-animals." 



All the old distinctions between plants and animals, 

 e.g. power of movement, once supposed to be a 

 characteristic of the latter, have had to be discarded 

 as innumerable exceptions to such rules have come 

 to notice. 



Moreover, the jelly-like colloids, about which so 

 much has recently been said, are very similar in 

 the case of minerals, plants, and animals, so that, on 

 a physical basis, life— which is even accredited 

 by some to minerals — has three types of manifesta- 

 tion. In the mineral each type follows certain 

 fixed laws of crystallisation, and once this is accom- 

 plished its work is done so far as we at present 

 know. A plant also has a definite mode of develop- 

 ment, and exhibits definite forms of living activity 

 continuously. Animals again develop in their way 

 activities of a kindred kind. Thus all three grow, 

 divide, multiply, and exhibit affinity for kindred 

 forms along certain lines. 



