Ward— Symbiosis. 555 
It has been proposed to apply the term Metabiosis to such 
cases. 
It must not be forgotten that there are extremes in another 
direction, where one of the two associated organisms is 
injuring the other, as exemplified by many parasites, but these 
cases I leave out of account here. This state of affairs has 
been termed Antibiosis . 
It seems not impossible that the biological relationships of 
these cases one to another could be shown thus : — 
Antibiosis. Symbiosis. 
Disjunctive — association. 
The Physiology of Symbiosis. 
It will be an interesting exercise to see if we can get any 
further glimpses into the physiology of the phenomenon of 
Symbiosis. 
When we come to inquire as to the processes which lead to 
enhancement of the functional activity of one organism by 
another living symbiotically with it, the matter presents many 
difficulties ; for it is at the outset quite obvious that many 
things are possible, and it soon becomes evident that a tangle 
of complexities lies before us, as always in the inter-relations 
between associated biological units. We need go no further 
than the examination of the possibilities in the inter-relations 
between a weed and a cultivated plant, or between two trees 
in a forest, for illustrations of this truth. 
Confining attention for the moment to closely associated 
symbionts, such as those composing a Lichen, the ginger-beer 
plant, or a clump of symbiotic Bacteria or Fungi, researches 
have made it practically certain that the provision of definite 
