HOMING OF SEA-SWALLOWS 7 



It is a familiar step in scientific method to try to 

 bring an obscure fact into line with others of an 

 approximately similar kind, and this must be done 

 in the case of the homing terns. In this connection 

 it is unfortunate that the data in regard to homing 

 dogs and cats and other mammals are not in a form 

 suitable for scientific purposes, and that crucial 

 experiments to show what untrained homing pigeons 

 can do are lacking. 



Exceedingly careful experimental work has been 

 done with ants and bees, which find their way 

 home successfully within a limited radius, and the 

 balance of evidence inclines to the conclusion that 

 most of the phenomena can be explained by the 

 gradual registration of various sets of stimuli 

 olfactory, tactile, visual, and kinaesthetic. Here 

 also, however, there are residual phenomena at 

 present as inexplicable as the homing of the terns 

 from Galveston to the Tortugas. Professor Watson 

 holds the chair of Experimental and Comparative 

 Psychology at the Johns Hopkins University, and 

 his experimental study of the homing terns is 

 marked by a greater psychological subtlety than is 

 usually to be found in the adventures of zoologists 

 in similar fields. Thus it is interesting to notice his 

 careful observations on the duration of the nesting 

 impulse when the normal activities have been inter- 

 rupted. He finds that it remains strong for two or 

 three weeks ; and this should be borne in mind, for it 

 gives an illuminating significance to the homing of 

 the sea-swallows. They are returning to their nests, 



