216 ZOOLOGICAL GLEANINGS 



of giving notice that its burrow was occupied — or, as 

 Mr Stebbing has expressed it, that it was *'not at 

 home " to callers ; and I think that this consideration 

 gives us a clue to the use of the stridulating mechan- 

 ism. At anyrate I was often able, after my first 

 accidental discovery, to elicit the sound, by catching 

 one of these crabs and forcing it into a burrow which 

 I knew was already occupied : the intruder would never 

 go far in, but would crouch just inside the mouth of 

 the burrow, and if it were made to travel deeper, 

 then the voice of the rightful owner would be heard 

 in indignant remonstrance from the depths. It does 

 not follow from this argument that the vocal mechan- 

 ism originated for this special purpose, or that it has 

 no other use ; this, for instance, may not be its sole 

 function in the case of the large grey ocypode crab 

 ((9. ceratophthabniis), which, so far as my observation 

 goes, does not always burrow deeply, and yet pos- 

 sesses a particularly perfect vocal organ, and, accord- 

 ing to Dr A. R. Anderson, can make a loud croaking 

 noise with it. By the grey ocypode crab it may 

 perhaps be used for scaring enemies : this is an 

 obvious explanation ; but that enemies, as goodman 

 Dogberry's watch might urge, will not always be 

 scared by noises is, I think, evidenced by the follow- 

 ing digression. 



In my aviary I have had for a long time a white- 

 cheeked bulbul, who is as bold as he is fastidious, 



