CHAPTER LXIII 

 ASSOCIATION OF ORGANISMS SOCIAL BACKBONED 



ANIMALS (VERTEB^ATA) 



That many backboned animals are of gregarious habit is too 

 well known to require emphasis. Our vocabulary includes many 

 words signifying communities of animals, e.g. we speak of a " shoal " 

 of fishes, a " flock" of birds, a "pack" of wolves, a "herd" of 

 antelopes, and so on. The societies of which the existence is 

 implied by many such words exhibit a type of communal life 

 differing greatly from that described for insects, and one that is 

 in some respects less interesting, except in so far as it throws 

 light on the problems of sociology, with which all intelligent 

 persons are more or less concerned. The complex conditions 

 resulting from numerous individuals living together have not 

 here led to profound anatomical specialization, as they have in 

 the case of such insects as ants. 



SOCIAL FISHES (PISCES). That so many Fishes should be 

 associated together in shoals would seem to be dependent in many 

 instances on the place and manner of spawning. In ordinary 

 bony fishes (Teleostei) the eggs are nearly always fertilized 

 externally, and it is obvious that this process is facilitated when 

 numerous individuals seek the same locality for the purpose. The 

 Herring (Clupea harengus], fig. 1102), for example, approaches 

 our shores in order to deposit its eggs in shallow water, where 

 they adhere to various objects ; the Salmon (Salmo salar) ascends 

 rivers for the same purpose; and the Common Eel (Anguilla 

 vulgaris) migrates in vast numbers to the deep sea in order to 

 spawn. How far the movements of migratory fish involve 

 division of labour is not at present known. It is not impossible 

 that some of the older individuals may act as "leaders", though 

 this is little more than a conjecture. 



The gregarious habit of many predaceous fishes, such as 

 Sharks, Dog-fishes, and Mackerel, may conduce to success in 



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