THE ZOOLOGIST 



No, 884.— February 15th, 1915. 



I - I 



THE SENSE OF DIRECTION. 



By J. M. Dewar, M.D. 



The " sense of direction " is a term used to denote the unknown 

 means whicb enables birds and other animals to return to the 

 localities they have left. The phrase also applies, though with 

 less propriety, to the mechanism by means of which migratory 

 animals proceed to regions they do not know, whether these 

 regions have been occupied by the animals' progenitors or not. 

 In the observations herein recorded the sense of direction is 

 considered from the aspect of the animals' environment. The 

 environment plays a part in the formation of the guiding 

 mechanism by providing data which may be used by the 

 organism in finding its way from one place to another. As it 

 happens, the immediate problem of a directive sense really turns 

 on the nature and extent of the external factors employed. At 

 the same time, the value of the possible factors can only be 

 determined when due regard is paid to the kinds of sensory 

 organs possessed by the animals, and also to the probable 

 degree of efficiency which the sensory organs concerned and the 

 associated nervous processes attain. 



Regarding the nature of the directive mechanism two historic 

 theories may be said to hold the field. The one, strange to say, 

 has been supported mainly by workers with insects, and is briefly 

 a " memory of localities," or a " knowledge of landmarks " ; the 

 other has been applied conspicuously to the higher animals, and 

 is a capacity to sense the position of the objective in terms of 

 Zool. 4th ser. vol. XiX., February, 1915. E 



