68 SMELL, TASTE, ALLIED SENSES 



garded as possessing powers of olfaction fairly compar- 

 able Avith those of the higher forms. This opinion is in 

 entire harmony with the well known fact that fishes, 

 especially sharks, can be drawn from a long distance by 

 ill smelling bait or by oily fish carcasses ground up and 

 thrown into the water as in the practice of chumming. 

 The extremely small amount of substance needed in these 

 operations agrees well with what is known of olfaction 

 among air-inhabiting vertebrates and reaches almost in- 

 finitesimal proportions as is indicated by the work of 

 Olmsted (1918) on Amiurus. 



The water-inhabiting stages of amphibians will doubt- 

 less be found to exhibit the same type of olfaction as 

 that seen in fishes. This is already clearly indicated by 

 the work of Copeland (1913) on the newt Diemyctylus 

 and of Eisser (1914) on tadpoles. 



The opinion that fishes possess powers of olfaction 

 comparable with those of the air-inhabiting vertebrates, 

 though rejected by many of the older writers, has been 

 accepted in recent years by Baglioni (1913) and by 

 Luciani (1917). In fishes there can be no doubt that the 

 stimulating material for the olfactory organs is carried 

 in the current of water that is passing more or less con- 

 tinuously through these parts. Since in air-inhabiting 

 vertebrates the stimulating materials are caught on the 

 watery mucous of the olfactory surfaces, it follows that, 

 as Durand (1918b) has recently declared, the olfactory 

 stimulus throughout the whole range of vertebrates is 

 material in a state of solution and not simply a gas or 

 a vapor. This conclusion is in agreement with the 

 opinion expressed many years ago by Johannes Miiller. 

 Henning (1916), some time since called attention to the 



