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 \ve 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 ; hut 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-waU, 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 m which it exists. If these organs are connected 

 with the auditory sense, the opinion, held by Carus, Straus-Diirckheim, Oken, Bur- 

 meister, and Rennie and Kirby, that the antennae are organs of hearing, wall not be 

 without foundation. In considering the function of these structures, we must bear in 

 mind that aU 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 throu2;h a membrane and a stratum of fluid. 



The carefid anatomical examination of the antennae 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 ;jth and |th-inch objectives. 



Note. — Since the reading of the above paper, I have seen (through the kindness of 

 Sir. J. O. Westwood) a copy of the rare work of Erichson, " Dissertatio de Tabrica 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. 



