THE EVIDENCE OF THE OLFACTORY APPARATUS 



2 3 l 



gives a satisfactory reason for its appearance in the lowest verte- 

 brates as an unpaired median organ ; equally so, the history of the 

 camerostoine itself supplies the reason why the olfactory nerves are 

 double, why the organ is in reality a paired organ and not a single 



Fig. 102. — Thelyphonus. (From the Royal Natural History.) 



median one. Thus, in a sense, the grouping of the fishes into Mono- 

 rhinae and Amphirhinse has not much meaning, seeing that the 

 olfactory organ is in all cases double. 



The evidence of the olfactory organs in the vertebrate not only 

 confirms, in a most striking manner, the theory of the origin of the 



