RELATIONSHIPS IN THE ENVIRONMENT 137 



pied, the conclusion seems inevitable that we 

 have here the determining condition which 

 renders the instinct susceptible to appropriate 

 stimulation. 



There remains the female. I place her last 

 in order of importance, not because I regard her 

 influence as of small consequence, but because 

 the evidence is of a varied and complex kind, 

 so much so that it is difficult to ascertain by 

 observation just how far she is a situational item. 

 It will be remembered that the only direct 

 evidence we had of such influence was a 

 deterioration or, in some instances, a complete 

 cessation of vocal manifestation. Clearly then 

 we are confronted with a relationship of a 

 different kind from that which we have been 

 discussing ; for not only is anything in the 

 nature of stimulation absent, but, and this is a 

 remarkable fact, the other items in the environ- 

 ment which formerly evoked response no longer 

 do so in quite the same way. Is there any 

 awareness on the part of the male of the relation 

 between his voice and the mate that is to be, or 

 is it merely that as the sexual situation increases 

 in complexity some inhibiting influence comes 

 into play? These are questions which lead up 

 to difficult problems. But it is no part of my 

 task to discuss the psychological aspect of the 

 behaviour ; my purpose is merely to show that 

 the situation on the arrival of a female undergoes 

 marked modification, that the instinct of the 

 male is then less susceptible to stimulation, and 

 that the factors in the external environment 



