ill ON THE PHYSICAL BASIS OF LIFE 137 



catch the murmur of these tiny Maelstroms, as 

 they whirl in the innumerable myriads of living 

 cells which constitute each tree, we should be 

 stunned, as with the roar of a great city. 



Among -the lower plants, it is the rule rather than 

 the exception, that contractility should be still 

 more openly manifested at some periods of their 

 existence. The protoplasm of Algoa and Fungi 

 becomes, under many circumstances, partially, or 

 completely, freed from its woody case, and exhibits 

 movements of its whole mass, or is propelled by 

 the contractility of one, or more, hair-like prolon- 

 gations of its body, which are called vibratile cilia. 

 And, so far as the conditions of the manifestation 

 of the phsenomena of contractility have yet been 

 studied, they are the same for the plant as for the 

 animal. Heat and electric shocks influence both, 

 and in the same way, though it may be in different 

 degrees. It is by no means my intention to sug- 

 gest that there is no difference in faculty between 

 the lowest plant and the highest, or between 

 plants and animals. But the difference between 

 the powers of the lowest plant, or animal, and 

 those of the highest, is one of degree, not of 

 kind, and depends, as Milne-Edwards long ago 

 so Avell pointed out, upon the extent to which the 

 principle of the division of labour is carried out 

 in the living economy. In the lowest organism 

 all parts are competent to perform all functions, 

 and one and the same portion of protoplasm may 



