Summary and Discussion 217 
the two eyes. This is a marvelous feat. We can tell the direc- 
tion whence comes a sound only by turning the head to and 
fro and focusing, as it were, the two ears on the sound. This 
seems unbelievable, yet we do it every day. In like manner 
we turn our heads this way and that in an attempt to de- 
termine from which direction the odor is strongest, or we feel 
the breeze, the vehicle of odor. The olfactory apparatus with 
which we are now equipped functions very poorly in helping 
to determine the direction of an object emitting an odor. Our 
receiving organ is merely a single immovable area of mucous 
membrane, within the head, where the air drawn in by respira- 
tion may touch it. Now let us imagine ourselves equipped with 
such olfactory organs as he ingeniously describes for these 
moths, ‘‘ a branching olfactory system turned inside out.’’ This 
would be a pair of external olfactory organs, much branched, 
symmetrically placed on the body as are our eyes and ears, 
mobile as are our eyes, and lastly, extending out in front of 
us one-fifth the length of our bodies. It is easy now to under- 
stand how such an apparatus could serve the organism better 
than either visual or auditory powers (as we know them) in 
guiding it to the source of the emanations. There is reason to 
believe that wonders would be accomplished by means of such 
a mechanism which would far exceed the marvels of sight and 
hearing. But, we must not forget, while this apparatus would 
be more powerful or efficient in detecting directions, its scope 
would be limited to a narrower field, because, unlike light rays 
or sound waves, which radiate in circles, odors are carried on the 
wind in a stream in only one direction. The greatest distance at 
which Man’s degenerate olfactory sense will function is not 
known to me, but I once heard a man, whose scientific accuracy 
could be relied upon, say that in the wilds of Montana, where 
only wood was used for fuel, he had often smelled coal smoke 
from a train from a distance of fourteen miles, in the clear air. 
Thus the ‘‘magie’’ and ‘‘mysterious sixth sense’’ which have 
been adduced to account for the attraction of these moths to their 
mates may readily be brought within our comprehension. I 
still maintain, however, that the creatures do not come ‘‘from 
the ends of the earth,’’ but that their flight in this quest is 
limited by the area of dissemination of odor in currents of air. 
