174 INTERNAL ANATOMY OF INSECTS. 
whose metamorphosis is semicomplete*, differ widely in 
their system of muscles from perfect insects, I shall be- 
gin my observations with them. 
We owe by far the most accurate and detailed ac- 
count of the muscles of larvze to the illustrious Lyonnet, 
who, with incredible labour and patience without ex- 
ample, dissected the caterpillar of the Cossws, and has 
described every air-vessel, every nerve, and every mus- 
cle that could be detected by the microscope. Cuvier 
also has given a description of the muscles not only of 
caterpiilars, but of the larvae of the Lamellicorn beetles, 
the Hydrophili, and the Capricorn beetles». From these 
sources are derived what I have now to lay before you. 
If you look at one of Lyonnet’s plates‘, the layers of 
longitudinal muscles look like so many parallel ribands, 
others run in an oblique, and others again in a ¢rans- 
verse direction’. He divides them into dorsal, ven- 
tral, and lateral muscles*, terms which sufficiently ex- 
plain themselves. Of the longitudinal muscles there 
are four principal rows‘, the others are more numerous. 
The principal object of these muscles, which are flexors 
and extensors, is to shorten or lengthen the body, or to 
act on any particular segment as the circumstances of 
the animal may require. I shall not here notice the 
muscles of the head and legs, as they are not remarkably 
different from those of perfect insects. The prolegs are 
moved by ¢wo muscles—the anterior one covering in 
part the posterior—of a remarkable structure: one of 
their points of attachment is by many branches or tails 
| Vous lpaays > Anat. Comp. i. 432—. 
© Anat. t. vu. f. 2. left hand. a Jbid. right hand. 
© Tbid. 115—. * Cuy. ubi supr. 
