MUSCLES OF THE LOCUST. 
195 
fined to the larger branches. My observations on the grasshoppers en- 
tirely confirm Lubbock's opinion, and probably his Conclusion may be 
safely made general for all insects. 
Air-sacks and spiracles. — Concerning the latter I have made no obser- 
vations, considering that an account of their structure belongs rather 
to the anatomist. Of the air-sacks I have only to say that in them the 
spiral filament is wanting, their inner walls being thrown up into quite 
high and somewhat irregular folds, but concerning the histological ele- 
ments of the sacks I can add nothing to what is already known. The 
absence of the spiral thread had already been noticed by the older 
authors. 254 The true air-sacks must be distinguished from simple tracheal 
dilatations. 
MUSCLES. 
By far the majority of the muscular fibres in Caloptenus and (Edipoda 
are transversely striated. Examined with a high power they are found 
to resemble closely the fibres of the common water-beetle, which has been 
so often figured and studied. 255 First there is a broad 
dark band, then a broad light band, which is, however, 
divided in two by a narrow dark line, just as in the 
fibres of HydropMlus, figured in the accompanying wood- 
cut. 
The way in which the muscular fibres are grouped 
together varies very much in different parts of the body. 
For instance, in some of the muscles of the head the 
fibres are not collected in bundles, but are more or less 
isolated, as appears with the utmost distinctness in a 
fibre of HydrophUus transverse section like Fig. 5, whde the muscles of the 
picens.-AfterMinot.^i lorax form bundles of more or less cylindrical form, as 
appears in Figs. 9 and C r. m. The single fibres are not round, as might 
be thought upon looking at one spread out longitudinally, but polygonal 
in section, as is seen in Fig. 5, the corners being rounded off. They are 
commonly four-sided, but sometimes three or five-sided. In every mus- 
cular bundle there are to be seen oval nuclei, whose long axes lie more 
or less nearly parallel with the direction of the muscular fibres. The 
nuclei are small and flattened, slightly granular, and many of them (Fig. 
9) contain a small eccentric nucleolus. They are situated on the surface 
of the fibres, to which I think they belong, though they are perhaps 
the nuclei of the sarcolemma. 
Besides the striated muscles there are also smooth fibres to be found 
around the intestine, as wfll be more particularly described hereafter. 
254 Burmeister : Manual of Entomology, translated by Shuekard, p. 178. 
^Hanviar: Traite Technique d' Histologic, p. 477 ff. 
Dr. T. Dwight: Structure and action of striated muscular fibre; in the Proc. Boston S. N. H. (1873- 
*74), vol. xvi, p. 119. 
Engelmann : Pliiger's Archiv. fur Physiologic, Bd. vii, pp. 33 and 155, and Bd. xviii, p. 1, and many 1 
others. 
