386 DR. J. B. HICKS ON THE ORGANS 



of their being auditory organs ; whilst, on the other hand, we have Lyonet, Eobineau- 

 Desvoidy, Kiister, Erichson, and Vogt in favour of their being olfactory organs. In point 

 of number, the majority are evidently in favour of their being organs of hearing, though 

 it appears to me that some on either side base their opinions on but slender foimdations, 

 and that the most important advocate on the olfactory side, Erichson, has formed his 

 opinion upon an imperfect knowledge of the true nature of the organs : he has thought 

 them to be closed perforations opening internally ; whilst I have, in the paper mentioned, 

 shown them to be closed sacs, sometimes considerably convoluted, to the inner aspect of 

 which the nerve passes. I shall, in the course of the present paper, show that by no means 

 in aU cases is the closiug-in membrane thin and delicate, but that in some insects it is 

 tliickened and even raised into a conical and hair-like eminence ; his arguments, therefore, 

 regarding its analogy to the pituary membrane clearly cannot hold. None of these writers, 

 and, so far as I am aware, no one else, had at the time when my former paper appeared 

 pointed out these closed, chambered sacs ; and it is evident that the opinions concerning 

 tlie functions of the antennjs, hitherto entertained upon an imperfect knowledge of their 

 structure, will undergo considerable modification when the structures I have already, and 

 those which I am now about to describe, are duly considered and re-investigated. 



I shall now proceed to the detailed description of the other antennae which I have 

 examined since my last paper. At that time I had not investigated the antennae of the 

 Coleoptera to any extent ; but I find they form no exception to the rest of the Insecta. 



1st. In Necrophora Vespillo the organs are only found on the last three joints, two of 

 which are foliaceous, while the terminal one is rounder and pointed at the apex, forming 

 the club or clava ; and a fourth, foKaceous joint does not possess these organs. 



The sacs are found on both sides of the leafy joints, and all round the terminal one, 

 though they are larger on the back. At A. fig. 1 (PL LXVII.), I have shown the surface 

 enlarged, with the covering-in membranes and position of the hairs between them. At 

 A. fig. 2. is the section of the same. The average diameter of the sacs is about 3x50 inch. 



The distribution of the nerve, spreading by many branches throughout the breadth of 

 the joint, can be seen by focusing for the centre of the lamella. This antenna is men- 

 tioned by Erichson, who, after describing its form, says of the last three joints, " Testa ei 

 est poris subtilissimis creberrimisque perforata, reUctis nonnullis areis minutis im- 

 pressisque, e quibus setula nascitur " {op. cit. § 10). It is these pores I have drawn at 



A. fig. 2, showing a sac which can be clearly made out in the bleached antenna. 



In the genvis Silpha there are eleven joints : the last three are dilated and covered with 

 fine haii's ; and scattered equally over the surface is to be found a number of sacs, one- 

 fifth less in quantity than the hairs, B. fig. \ b b. Besides these, there are larger sacs, 



B. fig. 1 a a, principally foimd on the terminal joint, about twenty-four in nmxiber. These 

 show clearly the form of the organs from above, and at B. fig. 2 their nature can be 

 further understood in section. The covering-m membrane is delicate, and rises as a low 

 cone from the general surface-level; between the organs the hairs arise and overhang 

 them. The diameter of the larger ones at the surface is xVe inch. This is the character 

 of the antenna throughout all the genus, so far as I have ascertained. 



In Creophilus, and probably in kindred genera, the organs are found only on the 



