378 DR. HICKS ON THE NERVE AT THE BASE OF THE HALTERES, AND ON 
This can be well observed in Rhingia rostrata and JEJristalis tenax. (See figure.) 
The nerve in the subcostal nervure is disposed in a somewhat similar manner. But in 
many instances I have found the ganglionic enlargement to possess more than one 
nucleus ; two or three apparently coexist in the Coleoptera (see a, figs. 4, 5, 6). The 
distal end of this enlargement tapers off to a rather fine extremity, so that it may pass up 
through the canals which pierce the integumental layers. 
The mode of termination in these nerves points out a homology to the termination of 
the optic nerve, as seen in its development in insects, and is, indeed, probably the method 
by which all nerves of sensation end, as has been shown by M. N. Jacubovitsch in the 
Comptes Rendm, May 7, 1860, p. 859. (See ' Microscopical Journal,' April 1861.) 
In some — the Saw-flies for example — the ganglionic enlargement is not elongated, but 
applied immediately beneath the canals ; so that, crowding as they do together, the whole 
seems as a compact layer of ganglionic cells. 
The outer nerve-sheath is attached to the edge of the skin-canal, as is shown in figs. 4, 
5 & 6, reminding one of the condition of the nerve-sheath of the compound eyes by which 
it attaches itself to the facetted cornea. 
We are indebted to Leydig for the additional knowledge of the ganglionic enlargement 
at the termination of the nerve supplying these structures *. 
structures *. Upon reviewing my papers, 
he states also that he has found little conical " pegs or rods " (" Stifte, Stabchen") with 
their bases towards the integument, which are situated in the extremity of the nerve, one 
or two in each. These, I must confess, after a very careful search through numerous 
specimens (many being the same as those in which he describes them), I have been unable 
to discover, and am therefore under the impression that he has fallen into some erroi 
the more so as he admits that it was only after a dozen trials that he himself succeeded. 
It is a difficult thing to prove a negative ; but, though I have frequently traced the nerve 
to its very end, I have failed to distinguish any such structures as the " Stifte " or " Stab- 
chen," either in specimens just killed or kept in spirit for different periods. I suspect 
that the method which he adopts of pulling out the nerve, by withdrawing the organized 
layer lining the integument internally and which passes within and lines the tube 
(skin-canal), has possibly led to the appearances described by him. I have noticed in 
the larger beetles a condition which renders this highly probable. Be this as it may, 
I have already done, an important senson 
there can be no hesitation in «„ & 
function to the organs taken as a whole. 
same 
the 
Leydig is under the impression that they are of the 
hinder part of the thorax in the Acridce, &c. first pointed out by Miiller, which he 
siders an organ of hearing. That they may be homologous to those in the Acrid", wot 
seem to derive some confirmation from the circumstance that he has not found Muller 
the same part in other insects, while I have not found those I have pointed oi 
ild 
in 
the wings of the 0/ 
But are they, therefore, auditory organs ? Have they any similarity to what we know 
of this organ in the Invertebrata ? I confess my inability to see any resemblance beyond 
■ 
* Reichert und Du Bois-Reymond's Archiv, 18G0, No. 3, p. 299. 
