xlv 



w. 



NORMAL VARIATIONS OF SPECIES. 



Living in the same locality. 

 Examples taxonomically arranged. 



Living in different localities. 

 Examples taxonomically arranged. 



X. 



ASSOCIATION OF DIFFERENT SPECIES, WITH 

 OR WITHOUT MODIFICATIONS OF STRUCTURE. 



Commensalism. 



Association of two species, from which one (the guest) con- 

 stantly found so associated derives advantage without injuring 

 its host. 



Examples arranged according to taxonomic position of guest. 



Symbiosis. 

 Association of two or more species for the advantage of all. 



Examples arranged according to taxonomic position of dominant 

 form. 



Parasitism. 



Association of two species, of which one, the guest, derives 

 advantage at the expense of the other, its host. 



Examples arranged according to taxonomic position of guest, 



