The Organism ami its Major Parts 37 



given plant are treated as though they were distinct, ulti- 

 mate data, whereas they certainly are not. The term 

 ^'symbiosis" was introduced into biology exactly for the 

 purpose of expressing the fact that individual organisms, 

 usually of very distinct species, get together in an intimate 

 relation wherein one or both members of the partnership 

 gain some advantage, each at the same time preserving its 

 unmistakable identity. There is certainly not the slightest 

 evidence that the asexual and sexual parts of plants were 

 origin all}^ independent of each other in this way. 



Let us accept momentarily (since his speculation is de- 

 pendent on our doing so) Mr. Davidson's contention that 

 "germ-cell must develop from germ-cell, bud from bud, in- 

 dividual from individual." Even so, no biologist who is a 

 genuine believer in organic evolution, that is, in the teach- 

 ing that all organic kinds have descended from ancestors of 

 different kinds, can allow that "much that has been dark 

 in the vegetable world" is made any less dark by the as- 

 sumption of such a fundamental independence of germ-cells 

 and germ-buds and "individuals" until he is informed as to 

 the ancestry, not only proximate but remote, of germ-cells 

 and germ-buds and "individuals." 



The kinship between these modern speculations about sym- 

 biosis and an ancient notion due, it seems, to Empedocles, 

 comes to light at this stage of the discussion. What that 

 notion is we shall see presently. Mr. Davidson's symbiosis 

 theory of plants involves, he points out, his theory of plant- 

 agens, which last theory involves, as he rightly says, the 

 conception that "germ-cell must develop from germ-cell, 

 bud from bud, individual from individual." But any ten- 

 year-old farmer's son may know this statement is not true. 

 Keeping the form though not the meaning of Davidson's 

 expression, such a boy can assert that germ-cells develop 

 not only from germ-cells but also from buds, and that buds 

 develop not only from buds but also from germ-cells. 



