152 DR. J. B. HICKS ON A NEW STRUCTURE 
As in some of the Diptera and Lepidoptera, so in this species, the antenna has cavities 
in which we can detect from three to ten organs similar to those on the outside. 
With regard to the physiological relations of these organs, I think we may perceive in 
them a structure analogous to that of the reputed auditory organs at the base of the 
antennules in certain Crustacea; but whether the resemblance be sufficient to allow us to 
conclude that they have a similar function, it is perhaps premature to assume. Their 
essential parts seem to be, a cavity in the antenna-wall, filled with fluid, closed in from 
the outer air by a very delicate membrane, and to the back of which a nerve certainly 
proceeds. . There seems to be some correspondence between the chain of minute bodies 
passing through the cavity in the Grasshoppers, and the otolithes in the Crustacea; but at 
present it is only in this tribe I have found such an arrangement, though subsequent 
observations may extend the number in which it exists. If these organs are connected 
with the auditory sense, the opinion, held by Carus, Straus-Dürckheim, Oken, Bur- 
meister, and Rennie and Kirby, that the antennæ are organs of hearing, will not be - 
without foundation. In considering the function of these structures, we must bear in 
mind that all the auditory organs hitherto discovered in the Invertebrata have been in 
aquatic animals, and consequently, when the elements of an auditory organ are found in 
an air-breathing animal, it will be necessary to consider the difference between the force 
with which sound is transmitted from water to water through a membrane, and through 
the same from air to water. If we assign an olfactory function to these organs, one 
difficulty presents itself, viz. that for the odorous particles to affect the nerve; they must 
reach it through a membrane and a stratum of fluid. 
The careful anatomical examination of the antennæ in all the genera of Insects would 
be a work demanding much time and many labourers, but productive of a rich harvest. 
If the method: of proceeding I have recommended be adopted, viz. the bleaching of the 
parts before they are placed in Canada balsam, I have no doubt many interesting varieties 
of these organs would be met with. The comparison of the habits of the insect with the 
structure of the antennal organs would afford a further confirmation of their nature. At 
the same time a comparison should be instituted between these organs and those I have 
before described in the base of the halteres and wings, especially with reference to their 
relation to the sense of smell. | 
I may add, that the magnifying powers required to show the structures in question 
best, are the 4th and 4th-inch objectives. - ! 
Note.—Since the reading of the above paper, I have seen (through the kindness of — 
Mr. J. O. Westwood) a copy of the rare work of Erichson, * Dissertatio de Fabrica et Usu 
Antennarum in Insectis," 1847, in which he mentions the existence of “ pores," which 
are shut by a thin membrane from the interior part of the antenna, and that their dispo- 
sition varied in different insects; but their peculiar form in Ichneumons, Wasps, &c.,also . 
the sacs, cavities, and nerves proceeding to them, he has failed to notice.—J. B. H. . 
