340 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
abdominal region is a curious fact of which no explanation can be 
offered. 
The direct descent of most of the imaginal muscles from larval 
muscles, which has here been shown, will help in solving some of the 
difficult problems of the comparative myology of insects, —a subject 
about which little is known. Hitherto the only basis of comparison be- 
tween the muscles of metabolic and ametabolic insects, or between the 
muscles of different metabolic insects, has been the origin and insertion 
of the muscles in the imago. No attention has been paid to the larval 
musculature, since this has been generally supposed to have no connec- 
tion with the imaginal. But, as this paper shows, there is a close 
connection between the larval and imaginal musculature in Coleoptera, 
and asimilar connection will probably be found to exist in most of 
the metabolic insects. With this relation as a basis for comparisons, 
the simpler conditions —the larval — may be used in establishing the 
homologies instead of the more complex, — the imaginal. And this, not 
only for comparison between different metabolic insects, but also between 
metabolic and ametabolic insects. 
A word ought, perhaps, to be added to meet the possible criticism, 
that in some of the muscles there are such radical differences between 
the conditions in the stages figured that the identity of the various 
muscles in successive stages is doubtful. In answer to this, it may be 
stated that not only the stages figured, but also several intermediate 
stages, have been studied. The dorso-ventral metathoracic muscles have 
been identified with the help of camera sketches in four individuals in 
stages of development intermediate between the stages used in making 
the reconstructions. Numerous other animals have been used in which a 
part of these muscles have been identified. The antero-posterior mus- 
cles are much simpler, and have been identified in as many as twenty 
cases. 
Part II.— Histology. 
A. HustroricaL SURVEY. 
This review of researches on the histological changes of the muscles 
during the metamorphoses of insects has been arranged in four parts 
corresponding to the four principal groups of holometabolic insects. Such 
an arrangement is used rather than asimple chronological one, because so 
little comparative work has been done that the mutual relations of the 
changes of the various groups are not entirely understood. The studies 
ein aan 
ee ee ee oe, 
