ZOOLOGY xxix 



with organic bodies, both Lamarck and Treviranus proposed 

 the name " biology " in the year 1802. Lamarck further 

 commits himself to the statement that all inorganic sub- 

 stances are derived from the exuviae of living bodies. He 

 believed that nature originally created only the most 

 elementary forms of hfe. These by evolution upwards led 

 to the animal and plant kingdoms: the decomposition of 

 these two types of organism gave rise to the third kingdom, 

 chiefly composed of minerals. 



He then has to define the difference between animals and 

 plants : he finds that irritability, or the power of response to 

 external stimuli, is a universal property of animals, and a 

 property which is invariably lacking in plants. Mimosa 

 pudica, the sensitive plant, gives him a certain amount of 

 trouble, but the apparent exception is explained by an 

 ingenious though (even for his time) highly speculative 

 theory. True irritability, characterised by an immediate 

 contraction on contact with a foreign body, is a property 

 which according to Lamarck is found in some part of every 

 living animal. In the second line of differentiation, he 

 names digestion and the power of locomotion as being charac- 

 teristic of the great majority of animals and wholly absent 

 in plants. 



Lamarck sees a new instance of the wisdom of the " sub- 

 lime author of all things " in the arrangements made for 

 preventing overpopulation of the earth by any one species. 

 Small animals, thou'gh multiplying with great rapidity, are 

 kept down by an immense mortality, in which they are 

 involved by the accidents of life, more especially the acci- 

 dent of being eaten by a larger animal. The larger animals, 

 which are not liable to serve as food for others, are main- 

 tained within their proper limits by a low rate of reproduc- 

 tion. Man alone might well multiply to cover the surface 

 of the earth : but he is himself his own executioner ; for 

 with the development of intellect comes the development of 

 passions, which ever lead to the reduction and Umitation of 

 his own species. 



