26o PIONEERS OF EVOLUTION. 



gist, describes to the writer the action of a kind oi 

 yeast upon a species of Daphnia, or water-flea. 

 Metschnikofif observed that these yeast-cells, which 

 enter with the animal's food, penetrate the intestines, 

 and get into the tissues. They are there seized upon 

 by the leukocytes, which gather round the invaders 

 in larger fashion, as if seemingly endowed with con- 

 sciousness, so marvellous is the strategy. If they 

 win, the Daphnia recovers ; if they lose, it dies. " In 

 a similar manner in ourselves certain leukocytes 

 (phagocytes) accumulate at any point of invasion, 

 and pick up the living bacteria," and in the success 

 or failure of their attack lies the fate of man. Which 

 things are fact as' well as allegory; and time is on 

 the side of the bacteria. For as our life is but a tem- 

 porary arrest of the universal movement toward dis- 

 solution, so naught in our actions can arrest the 

 destiny of our kind. Huxley thus puts it in the con- 

 cluding sentences of his Preface — written in July, 

 1894, one year before his death — to the reissue of 

 Evolution and Ethics: 



" That man, as a ' political animal,' is susceptible 

 of a vast amount of improvement, by education, by 

 instruction, and by the application of his intelligence 

 to the adaptation of the conditions of life to his 

 higher needs, I entertain not the slightest doubt. 

 But, so long as he remains liable to error, intellectual 

 or moral; so long as he is compelled to be perpet- 

 ually on guard against the cosmic forces, whose ends 

 are ndt his ends, without and within himself; so 



