its display continued hour after hour, without pause or 

 sign of weakening. The possible complexity of many 

 other organic forms, seemingly as simple as the proto- 

 plasm of the nettle, dawns upon one; and the compari- 

 son of such a protoplasm to a body with an internal 

 circulation, which has been put forward by an eminent 

 physiologist, loses much of its startling character. Cur- 

 rents similar to those of the hairs of the nettle have 

 been observed in a great multitude of very different 

 plants, and weighty authorities have suggested that they 

 probably occur, in more or les? perfection, in all young 

 vegetable cells. If such be the case, the wonderful 

 noonday silence of a tropical forest is, after all, due only 

 to the dullness of our hearing ; and could our ears 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 Algce 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 prolongations of its body, which are called vibratile 

 cilia. And, so far as the conditions of the manifesta- 

 tion of the phenomena of contractility have yet been 

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

 mal. 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 suggest that there is no 



