1882.] 
Sense of Smell in Insects. 
271 
and nothing else ; the rose-beetle, which consumes merely 
the neCtar and the pollen of a few species of flowers — all 
require an organ of scent not merely acute, but nicely dis- 
criminating. Accordingly we find them endowed with highly 
complicated antennae. Similar observations, which might 
be worked out to a greater extent than space here permits, 
all point in the same direction. We have therefore a case 
which falls under the method of “ concomitant variations.” 
We have evidence that a certain faculty varies in different 
inseCt groups. We see, further, that the development of a 
certain organ varies in a manner which may be pronounced 
parallel with the variation of the faculty. We are therefore, 
I submit, warranted in forming the provisional conclusion 
that the organ in question is the seat of the faculty in 
question. 
I will now consider some of the objections urged against 
the olfactory character of the antennae. It is maintained 
that a scent-organ must be placed in connection with the 
respiratory apparatus, so that a current of air laden with 
odoriferous particles may be drawn over its surfaces. This 
condition is essential, it appears to me, only when the organ 
in question is placed in the interior of the animal. An 
olfactory membrane placed in some deep cavity in the body, 
and not traversable by a stream of air, would be simply 
useless. But place the organ externally, where it freely en- 
counters the atmospheric currents, and can if needful be 
waved backwards and forwards in the air, and this objection 
falls to the ground. Nor does the dryness of the antennae 
seem a fatal objection. The entire body of inseCts is much 
drier than that of vertebrate animals or mollusks. 
There are those who maintain that the antennae are organs 
of touch. To this I reply that their excessive shortness in 
some species, and their delicate texture in others, renders 
them unsuitable for this function. In other species they are 
undoubtedly used as “ feelers.” But we must remember that 
in many Mammalia the nose serves this double function — 
e.g., in the horse, the pig, and the elephant. 
That they can be organs of hearing may be, I think, re- 
garded as discredited by the considerations already brought 
forward, as well as by the faCt that indisputable ears have 
been discovered in other parts of certain inseCts ; those espe- 
cially in which the faculty of hearing is most plainly present 
have their ears in the first abdominal ring just above the 
joint of the hind legs, and others in the tibiae of the fore 
legs. 
An argument in favour of the antennae being the seat of 
