220 SOCIAL LIFE IN THE INSECT WORLD 



offensive. I was amazed at my collection, which com- 

 prised the greater number of the hypogenous fungi of 

 the neighbourhood. 



What a variety of structure, and above all of odour, 

 the primordial quality in this question of scent ! There 

 were some that had no appreciable scent beyond a vague 

 fungoid flavour, more or less common to all. Others 

 smelt of turnips, of sour cabbage ; some were fetid, 

 sufficiently so to make the house of the collector 

 noisome. Only the true truffle possessed the aroma 

 dear to epicures. If odour, as we understand it, is the 

 dog's only guide, how does he manage to follow that 

 guide amidst all these totally different odours ? Is he 

 warned of the contents of the subsoil by a general 

 emanation, by that fungoid effluvium common to all 

 the species ? Thus a somewhat embarrassing question 

 arises. 



I paid special attention to the ordmary toadstools and 

 mushrooms, which announced their near advent by 

 cracking the surface of the soil. Now these points, 

 where my eyes divined the cryptogam pushing back the 

 soil with its button-like heads, these points, where the 

 ordinary fungoid odour was certainly very pronounced, 

 were never selected by the dog. He passed them dis- 

 dainfully, without a sniff, without a stroke of the paw. 

 Yet the fungi were underground, and their odour was 

 similar to that I have already referred to. 



I came back from my outings with the conviction that 

 the truffle-finding nose has some better guide than odour 

 such as we with our sense-organs conceive it. It must 

 perceive effluvia of another order as well ; entirely 

 mysterious to us, and therefore not utilised. Light 



