ON THE OLFACTORY SENSE OF BIRDS 121 



Table 2. Spontaneous reactions to olfactory stimuli of geese 



Table 3. Spontaneous reactions of two geese to skatole and vv'ater 



Probability for a random result p == 0.0937. 



and for formaldehyde to be samples from the same population. According 

 to the formula 



a:2 = 



n • n L^mA 



Zi + z; 



a value for A.'- of 27 was obtained, corresponding to a probability of 

 p =z 0.0007. Thus it is proved that geese behave differently when exposed 

 to skatole as compared to water. This can only mean that the geese have 

 shown an olfactory response to skatole. 



DISCUSSION OF THE RESULTS 



The last experiment seems to contradict the first mentioned experiments. 

 An explanation can be found in the central olfactory pathways. The secon- 

 dary and tertiary olfactory fibre bundles of the birds are, in contrast to 

 those in the mammals, little developed, particularly those ending in the 



