Anaholism and SpecialisafAon. 203 



character as plants to this association. The higher plants 

 would, through specialisation, increasingly lose the tendency 

 to form these katastates, except where they could be formed 

 and retained as protective poisons, or in some other condition 

 favouring the preservation of the species. 



As to the separate lines of evolution followed by plants 

 and animals, it is quite evident that once these tendencies 

 to divergence of specialisation were acquired, they would 

 gradually be increased by natural selection, according as to 

 what was most beneficial for each diverging type. That 

 primitive type, which could afford to wait for its food owing 

 to the small amount of waste it underwent, and from the 

 same cause could show the best account for it when it 

 obtained it, would have this property gradually increased by 

 natural selection, and its tendencies to katabolism would thus 

 be reduced more and more, impeding its powers of locomo- 

 tion. But when brought in contact with conditions that 

 were unfavourable for the continuance of its existing mode 

 of life, the tendency would be for it to show return to a more 

 active habit in order to procure an existence, and motile 

 zoospores would be liberated. The causes unfavourable to 

 its existence, apart from its being engulfed as food by some 

 other organism, perhaps a less common mode of death then 

 than later in the history of organisms, would chiefly come 

 from the inorganic changes in the outer world. Amongst 

 these, as an attempt was made to gain a littoral existence, 

 one of its greatest enemies would be dessication, and any 

 form that it could take which would resist dessication for a 

 while would prove of vast service. The tendency for resting- 

 spores to be formed by the conjugation of these zoospores 

 could be accounted for in this way. Among Algee these 

 resting-spores seem now to occur chiefly in the fresh-water 

 forms, and these forms would certainly seem to suffer most 

 from dessication. Through survival of the fittest these Algse 

 would acquire the possibility of living in drier situations- 

 The sexual plant, as constituted, would, however, be unfitted 

 for a continued existence under the adverse conditions of 

 dryness and quick changes of temperature found on land, and 

 would repeatedly find refuge in the formation of resting- 



