in the development of Unicellulars 33 



terms ^." Lowly as these forms of life appear 

 when compared with our own, still the 

 enormous diversity to be foimd among them, 

 their wide range in space and their prodigious 

 antiquity, together suggest that between the 

 highest of them and the very beginnings of 

 life lies a long, long history of " one kind of 

 behaviour after another." In the course of 

 that history functions were mechanized and 

 structures fixed. 



All this while the situation is that of our 

 imaginary immortal developing by intercourse 

 with its environment, save that here the im- 

 mortal is real and not imaginary; and also, 

 instead of remaining solitary, is continually 

 manifolding itself into new individuals who 

 start equipped with all its acquisitions. All 

 this while too the whole organism of every 

 individual is in touch with the environment 



^ J. Arthur Thompson, Heredity, p. 33. 



