XCUEJE 
33 
Intergangliomc Commissures. (PI. I. figs. 2 & 7.) 
It might have been expected that the tracheae on these organs would have resembled 
those on the ganglia, and at any rate that tracheae would either have been present or 
absent in all insects. Both suppositions, however, would have been wrong. The tubules 
in the ganglia are usually straight, while those on the commissures are generally waved, 
besides differing in other respects. Again, in Pentatoma and all the Lcpidopterous larva* 
which I have examined, the commissures are very richly supplied ; in Bombus, the Diptera, 
and some Coleoptera, they are less numerous ; while in some Coleoptera, the Orthoptera, 
Lepidoptera, and Neuroptera, the tracheae are either rare or altogether absent. This 
© 
com 
at least holds good as far as my observations go ; but the statement will no doubt b< 
modified by further investigations. 
Between two of the thoracic ganglia in the larva of Acheta I found one of the 
missures pretty well supplied with trachea*, while the other was quite free from them. 
Indeed generally throughout insects the tracheae on the two nervous columns are noi 
arranged in exactly the same manner. 
In Scarabmis, Necrophorus vespil/o, and N. humator, the tracheae on the commissures 
and on many nerves were in tufts resembling those of the ganglion, except that they 
are altogether smaller, that the tubules branch oftener, and that they are more waved. 
In Cemmbyx moschatus also the commissures were well supplied with tracheae. In Hy- 
ilrophilus piceus the tracheae were like those of Necrophorus, but in some cases I observed 
branchlets which did not form tufts. The tubules were numerous and very delicate indeed. 
In JIusca and installs the tracheae were in tufts, very much like those on the ganglia, 
but with straighter tubules. The nerves, however, were almost entirely free from tracheae. 
In Tipula the tracheae wer 
In the larva of Lucanus the commissures wer 
well supplied, but in Carabus, the larva of Lampyris, and in Forficula, both they and the 
nerves were almost entirely free from tracheae. In Acheta, Locusta, and Gryllus also, the 
abdominal commissures had only here and there a single trachea, which seemed as it were 
to have strayed out of a neighbouring ganglion. In these cases I have not examined a 
sufficient number of specimens to prove that these single tracheae are inconstant but I 
have little doubt that this is the case. The thoracic commissures of Acheta, and also of 
its larva, were provided with decidedly more numerous tracheae, which are a little waved 
and give out single branchlets which again divide once or twice. 
In Noctua the tracheae are like those of Acheta, but rather more numerous, two or 
three generally running nearly to the middle of the commissure. They are seldom, if 
ever, branched, and are almost straight. On those of Campcea margaritaria, Pieris napi, 
Hipparchia janlra, Callimorpha jacobcea?, and Pterophorus, I found no tracheae. On the 
contrary, in the larvae of Euplexia lucipara and Gonepteryx rhamni they were well sup- 
plied ; and in the larvae of Lasiocampa rubi and Mamestra they were very numerous both 
on the commissures and nerves. On the commissures of Bombus musconim they are nu- 
merous, waved, and generally in tufts consisting of a few branched tubules, sometimes 
even of only two. On those of Athalia spmarum, Tenthredo, Ichneumon (probably) ex- 
tensorius, and another small black species, I found none. On those of Ophion there 
VOL. XXIII. 
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