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their enemies. When a party of curlews {Numenius arquatd) 

 are feeding, it is almost a certainty that one of the number, by 

 means of some sense or other, will become aware of any danger 

 that is approaching and give warning to the rest. And the 

 sociability that thus protects them we cannot regard as entirely 

 instinctive : it is partly habit learned in each by the young from 

 their elders. And thus it comes about that the tradition of the 

 species to some extent decides the course of its evolution by 

 deciding the manner of life that its members are to lead. 

 Those to whom life in a community proves uncongenial probably 

 fall victims to enemies. 



" Can this newly discovered principle help to heal the feud 

 between the followers of Weismann (the Neo-Darwinians) and 

 the Lamarckians ? If it can, then the Lamarckians must have 

 a singular power of mistaking an utter rout for a compromise. 

 For what the new principle shows is not that acquired charac- 

 teristics can be transmitted, but that Natural Selection can, 

 without such transmission, do what Lamarckism claimed that 

 it had the exclusive right and power to do. Each generation 

 decides in the main the environment of the next, and insists that 

 it shall live in that environment. Those of the young survive 

 who, with the aid of some training, are able to accommodate 

 themselves to the environment in which they are put. The 

 similarity of environment in each generation leads to selection 

 for similar characteristics : modifications and accommodations in 

 the individual, though not transmitted, are followed by variations 

 and adaptations in the race, the very phenomenon which has 

 always been the Lamarckian's most formidable weapon. This 

 can now be explained on Neo-Darwinian principles, and if you 

 can show that your opponent's theory is not the only nor the 

 best way of accounting for the facts which he. himself adduces, 

 you cut the ground from under him. A smiile may perhaps 

 make it clear how the principle works. We may look upon a 

 species as a huge herd of animals that are being driven 

 along a road ; the driver being some impulse in themselves. 

 Numerous roads lead oiT on either side, and it is impossible 

 to say that one is the main road more than another. All these 



