SIMPLICITY OF THE LOWEST ORGANISMS. 5 



case it is impossible to suppose that they are only hur- 

 ried along by currents, and it is safe to conclude that 

 even these simplest organisms are gifted with the 

 power of independent motion. Of the nature of this 

 power nothing is very certainly known. The organisms 

 of which we are speaking belong to the lowest rank of 

 the organic world. They are living beings, for they 

 move, they grow, and they multiply ; they can be 

 killed, for instance, by boiling water, and their inde- 

 pendent motion then ceases. This is nearly all that is 

 known of them. Next to them rank organisms which 

 are somewhat more complex in structure. They are 

 small lumps of semi-fluid, granular matter, which is 

 called protoplasm. 1 This semi-fluid condition inter- 

 mediate between a liquid and a solid state is charac- 

 teristic of all organic matter. It is due to the absorp- 

 tion of water into the pores of a solid mass, which in 

 consequence swells and undergoes an intimate mixture 

 with the water, and in which the molecules can then 

 change their positions in the same way, though perhaps 

 not quite so easily, as otherwise is possible only in liquids. 

 A thin jelly-like clay would afford the best representa- 

 tion of this condition of aggregation of protoplasm. 

 A small lump of protoplasm of this sort may in itself 

 represent an independent living being, exhibiting vital 

 phenomena of such a kind that it is impossible to refuse 

 to call it an ' animal.' It moves by its own force, and, 

 as it would seem, voluntarily ; it imbibes matter for its 

 own nutrition from the surrounding liquid ; it grows, it 

 multiplies its kind, and it dies. The most evident mo- 



1 Sometimes, but not always, in addition to these fine granules, a 

 larger, bladder-like body, called the kernel or nucleus, is seen within 

 the mass. 



