The Relations of Living Beings

I N the preceding essays* we have considered the relations of living beings to space (as revealed to us by Palreontology) and to timeas shown us by organic geography. The inter-relations of living creatures, as enemies, as rivals, and as involuntary helpers, constitute 1\ third department of Hexicologyt not less interesting than the two others already treated of. There is one very general inter-relation which has been already pointed out,t namely that between animals and plants, for animals cannot subsist without feeding directly or indirectly on plants, while plants are nourished by the carbonic acid which the animal world gives forth in breathing. The inter-relations which are to be here considered however are of the more active character just referred to and result from predatory habits, rivalry, or unintentional assistance. These relations may be grouped in twelve sets of inter-actions, seven of them favourable and five unfavourable. 1. Thus, in the first place, one kind of organism may benefit another by serving that other as its food. 2. One living creature may benefit another by destroying direct enemies of that other, which if not destroyed would prey upon it. 3. An organism may benefit another by destroying indirect enemies of that other-that is by destroying rivals which tend to stave out, though not directly to injure, the organism thus helped. 4. One living creature may benefit another by involuntarily carrying it about, and so serving it as a vehicle for change of place. 5. One animal sometimes benefits another organism by involuntarily feeding it in the process of feeding itself or otherwise.