no LIFE : OUTLINES OF GENERAL BIOLOGY 



Many other instances may occur to the student, but one must 

 emphasise the jxjint that mere gregariousness is not in itself social; 

 there must be e\'idence of some corporate activity. A herd of cud- 

 chewing herbivores strikes the social note when there is anything 

 like combining against a carnivorous enemy, or posting sentinels, 

 or setting off on a journey with one accord. 



Among the social birds a prominent place must be given to the 

 rooks, the cranes, and the parrots — all of them big-brained. Large 

 numbers of sea-birds, such as gannets and guillemots, often nest 

 togetlier, but this may be mainly because there are not very many 

 suitable cliffs with nesting-ledges. Thus there are not in the world 

 as many as twenty breeding-places of gannets. But in these crowded 

 haunts there is almost no hint of sociality, except that the excited 

 throng, flying out when disturbed, must automatically serve as a 

 deterrent to predatory intruders such as falcons. And yet among 

 those birds that nest gregariously, such as cliff-swallows, the social 

 note is definitely struck when there is an organised, if not deliberate, 

 mobbing of birds of prey that dare to come near. From such simple 

 beginnings there is an inclined plane to the rookery, where concerted 

 action is common, and conventions are unmistakable. There seems 

 to be no doubt that pelicans sometimes make themselves into a 

 living seine-net, wading in a semicircle towards the shore and driving 

 the fishes before them. This successful first step in corporate action 

 may be contrasted with the beha\iour of herons, which always keep 

 themselves to themselves in their fishing, though we occasionally 

 see half a dozen at short intervals in a row. They are, of course, 

 gregarious in their nesting, and show some unanimity in their 

 routine through a long summer day. But the heronry is far below 

 the rookery as a social formation. 



But while there are well-known social mammals and social birds, 

 such as those above referred to, it must be admitted that sociality 

 is hard to find among reptiles, amphibians, and fishes. Perhaps this 

 is an indication that a certain fineness of brain and mind is a pre- 

 condition of social life. Perhaps it merely means that the need for 

 social combination has not become urgent at these lower Vertebrate 

 levels; and j'et there are many reptiles, amphibians and fishes which 

 have a very hard struggle for existence, and cannot find it easy to 

 keep their place in the sun. One would welcome even a secret society 

 among the New Zealand Sphenodons and other "living fossils" if 

 that would keep them from disappearing. 



No doubt there may be hundreds of frogs in a marsh or even on 

 a tree, and there seems a hint of communal singing in their sere- 

 nading, though it sounds cacophonous to our refined ears; but 

 that is, we think, the nearest approach to sociahty in amphibians. 

 There are places, in the Dalmatian Islands, for instance, where it 

 is difficult to pick one's steps among the welter of lizards, whose 



