184 MR. LUBBOCK ON THE CUTANEOUS MUSCLES 
No. 7 rises at the posterior end of 16, and passes forward and upward nearly to the 
upper end of 37. : 
Nos. 16 and 17 have coalesced. E 
Nos. 50 and 51 are even larger than usual, and pass quite back to the posterior end of - 
the segment. 51 is double in front and attached under 16. : 
Besides these muscles, there are attached to the upright wall of the end of the body, - 
and in a series along the lower middle line of the segment, a number of muscular fascicles 
which are distributed to the rectum and posterior parts of the alimentary canal; in the | 
same place also are situated the muscles which move the posterior prolegs ; I have not, 
however, examined these muscles with care enough to enable me to describe them satis- 
factorily. 3 
Comparison of the Muscles in different Specimens.—Any one who has carefully exa- 
mined Lyonet's drawings of the cutaneous muscles in the larva of Cossus ligniperda, or. | 
still better, has made himself acquainted with the organs themselves, must have been 
struck with amazement at their number and complicated arrangement. 1 | 
The muscles in most animals are penetrated by the arteries and capillaries, and are 
supplied by them with blood; but this not being the case in insects, it is perhaps neces- 
sary that their muscles should be divided into numerous fascicles, in order that the blood 
may have free access to them. "Whether for this or some other reason, they are in the 
shape of thin ribands, the thickness of which varies very much in different muscles and - 
in different parts of the same muscle, but is in the largest about 37th of an inch. 
The largest muscular fibres in man, which are not penetrated by blood-vessels, are, I : 
am: informed by Professor Huxley, goth of an inch in diameter. We can, however, - 
en argument from this comparison without knowing the permeability of the musde 
and the power of penetration possessed by the blood. It is also worthy of notice, that the 
pg of insects are separated into very small fascicles, as if, from the violent and - 
dre e muscles, their particles were more quickly deteriorated, and required - 
quently to be removed and replaeed by others. The muscles of 
insects, however, ar = : : TEC 
RR e not only very much divided, but are also very compliqués in their à 
e head and 
pourra qu’étonn 
de I 2 ^" yn 
ENER, e quil y en å méme qui le fixent à beaucoup moins." It might 
s in insect larvæ, as for instance 16, 17, 18, 19 and ~ 
of muscles rather than as whole muscles, and that i | 
very much diminished. | 
~h objection, we should expect to find these pu 
do so, R umber; and as, except in certain instances, they do = : 
he cui must, I think, admit that Lyonet was ini in his mode of estimating e 
. Some few, | 
however, of t d 
amount of thes. he smaller muscles do vary; and to determine the number and ; 
se variati ief object ; 
lons was my chief object in undertaking the present paper. 
