M. II. Rathke on the Respiratory Process in Insects. 91 
to the same spot on the opposite wall ; and of these, one is always 
placed where two segments are contiguous. Below them are 
the ventral chain and two long and wide trachez. When they 
contract, the abdomen is somewhat narrowed from each side. It 
is narrowed from below by numerous muscles, of which the first 
segment has two pairs, and all the rest, with the exception of 
the last, one pair. All these muscles unite the ends of the lower 
plates with those of the upper plates of the same segments : they 
lie close to the inner surfaces of the lateral soft spaces. Other 
much smaller muscles serve to draw inwards these soft spaces, 
which are of considerable width, and thus also contract the ab- 
domen from above and below. Three of these small bundles 
pass up from each end of the lower plates and attach themselves 
to the soft skin; but one such muscle comes from the extremity 
of [the upper plate of] each of the same segments and attaches it- 
self opposite to the first, also on the soft skin.» The abdomen 
may be shortened by several muscles which unite together its 
individual segments : of these, one pair always goes from the 
end of the lower plate of each segment to that lying imme- 
diately before it, whilst others, forming long and slender bands, 
unite the upper plates of each two segments, as in the Locuste 
(Gryll) and Acridia. 
The respiratory movements themselves are probably effected 
exactly as in the Locuste (Grylli) ; but the author had no oppor- 
tunity of observing A. campestris alive. 
In Acheta Gryllotalpa, Fab. (Gryllus Gryllotalpa, Lamk.), the 
skin of the abdomen is formed exactly as in A. campestris, but 
the muscular apparatus of this part is much simpler. The upper 
plates of the abdominal segments are united to each other as in 
A. campestris ; this is also the case with the lower plates, but the 
muscles of these are absolutely and relatively much broader and 
stronger. The muscles uniting the upper and lower plates are 
not of the same kind in all the segments; in the two anterior 
segments they are of the same form as in A. campestris, but much 
stronger; in the other segments they form broad bundles, of 
which some fibres run from the upper plate, and others from 
the lateral soft skin, to the lower plate, and of which some take 
a straight course, while others appear to cross. The specimen 
examined had been for several years in spirit, and had become 
extremely hard. 
The trachez in both species of Acheta are very wide, but never 
vesicularly dilated. 
§ 13. In the broad and rather depressed abdomen of Mantis 
religiosa the lower plates of the segments are nearly of the same 
length as the upper ones. At the sides a blunt edge is formed 
by them and the soft skin uniting them, Lach of the lower 
