ADAPTIVENESS AND PURPOSIVENESS 337 



of lining the interior with feathers there may be over two 

 thousand of them, of covering the outside with lichens 

 which make the nest almost invisible on the bough. There 

 is no doubt as to the adaptiveness of the chain of acts; it 

 seems clear that the work is without justification until it 

 is finished; we cannot make sense of the prolonged activity 

 unless we see the whole in the light of the final result which 

 is of great value to the individual bird, to the nestlings, and 

 to the species in question. But we are no longer so certain 

 that the bird's behaviour is actuated by perceived purpose. 

 We may know, for instance, that the bird never made a 

 nest or laid an egg before ; we know that there is a remark- 

 able rigidity in the routine which sometimes detracts from 

 its effectiveness; and that there are occasional aberrations 

 which suggest that the bird is not quite on the spot. In 

 other words, we are watching an instinctive routine with a 

 spice of intelligence. How far are we warranted in saying 

 that it is actuated by purpose? Can there be purpose which 

 is not clearly perceived? We propose to rank all such cases 

 under the rubric ' purposiveness '. It implies in the bird's 

 case a determined endeavour, obedience to an inborn inspira- 

 tion modified by intelligence, but we are not sure how far 

 the end is in view. 



Returning to the observations of Prof. J. B. Watson and 

 Dr. K. S. Lashley on homing terns, we have to interpret such 

 facts as these. A number of brooding terns are conveyed in 

 hooded cages on board ship for over four hundred miles 

 from the nesting island ; they are liberated in the middle 

 of the sea beyond all hint of land ; they set off at once for 

 home against a head wind ; some of them reach home safely. 

 How they succeeded we do not know; whether they are in- 

 fluenced by magnetic currents and the like we do not know; 



