370 IHE BEGINNINGS OF LIFE. 



plasmic tissue of various aquatic plants and animals 

 of a low grade of organization, that such living things 

 exist and die under the very conditions which might 

 have been imagined to be most favourable for the 

 occurrence of transformations in the matter of which 

 they consist. The living matter of these organisms 

 exists in a semifluid state, and is exposed, in com- 

 paratively small masses, to the influence of various 

 physical forces acting through the fluid medium in which 

 they are immersed. When units of living matter exist 

 as constituents of one of the higher organisms (in which 

 the actions of all the different parts of the body are 

 nicely balanced and subordinated), their individual 

 actions in different parts induce, and are necessary for, 

 the maintenance and increase of the whole as a whole. 

 But in one of the filamentous fresh-water Algse we 

 meet with such a mere aggregate of organic indi- 

 vidualities — of parts potentially separate — that when 

 the conditions of the medium in which it lives become 

 in any way unsuitable, its molecularly- mobile and im- 

 pressible tissue soon begins to feel the influence of 

 such change : modes of action and interaction are set 

 up between the organism and its medium which 

 speedily become quite incompatible with its further 

 existence as an Alga. The molecular changes in- 

 duced in its interior are of such a kind that the 

 several parts of each of the aggregates of which it 

 is composed first cease to work in harmony, and after- 

 wards may be still more modified, so as to make it 



