I 



ECOLOGICAL 109 



(11) Perhaps to be regarded as instances of discontinuous com- 

 mensalism are such partnerships as that between certain ants 

 and their associated Aphids with abundant honey-dew, or that 

 between other ants and minute guest-beetles, sometimes with 

 attractive exudations. 



(12) The series naturally ends in gregarious and social associa- 

 tions whose members are of the same kith and kin — in flock and pack, 

 in termitary, ant-hill, and beehive, in rookery and beaver village. 



The analysis given shows the complexity of inter-relations be- 

 tween organisms, and yet it is far from complete. It requires a large 

 addendum of "Miscellaneous Linkages". 



SOCIAL ANIMALS 



I. A thousand passengers on a liner make an isolated aggregate of 

 individuals, but they do not constitute a society. Yet if they were 

 wrecked on an uninhabited oceanic island, they would soon strike 

 the social note. That is to say, they would begin to show corporate 

 action. They would begin to act as a unity, as a whole which is more 

 than the sum of its parts. Similarly with animals, there is nothing 

 social in the multitude of mites in the cavern of a cheese, but even 

 a small community of ants is a societary form. Hard-and-fast lines 

 are impossible; aggregate shades into integrate; but there is no 

 mistaking even a feeble social note which is sounded whenever a 

 group of individuals begins to act as a whole, with some self-subor- 

 dination among the members. There may be a thousand barnacles 

 hanging from a floating log, but there is not in the whole quaint 

 company the sUghtest hint of the social. Yet beginnings are per- 

 ceptible when a troop of cuttle-fishes swim together harmoniously, 

 keeping together in one direction, flushing with colour-change at 

 the same instant. The simplest expression of the social is when a 

 number of normally solitary animals migrate together, as if moved 

 by a common spirit. A mass-movement of starving lemmings or of 

 still wingless locusts may be at no higher level than the disorderly 

 flight from a burning city, but a migration of reindeer or a march of 

 driver-ants is definitely social. 



2. A further step in the evolution of social life among animals 

 is illustrated by troops of monkeys, which sometimes combine to 

 raid an orchard; and yet more by the members of a beaver "village", 

 who unite to dig a canal through an island in a river: by a herd of 

 elephants, which can combine into a formidable charge; by the 

 winter pack of wolves, who hunt individualistically in the summer 

 time, or, in its way best of all, by the prairie-dog-like viscachas of 

 La Plata, that may even arrange an expedition to unearth an 

 adjacent colony whose burrows have been closed by the farmer. 



