26 INTERNAL ANATOMY OF INSECTS. 
animal in its new stage of existence, 1n which the an- 
tenne, eyes, and other organs of the senses, as well as 
the limbs and muscles moving them, and the sexual or- 
gans, being very different from those of the larva, and af 
not wholly new, yet expanded from minute germs to their 
full size, may well demand corresponding changes in the 
structure of the nervous system by which they are acted 
upon. 
But are these changes also concerned, as Dr. Virey 
conjectures, in producing that remarkable alteration 
which usually takes place between the énstincts of the 
larva and imago? In order to answer this question, it 
will be requisite first to quote the ingenious illustration 
with which this able physiologist elucidates his ideas on 
this point.“ The more readily,” he observes, ‘to com- 
prehend the action of instinct, let us compare the insect 
to one of those hand-organs in which a revolving cylin- 
der presents different tunes noted at its surface, and 
pressing the keys of the pipes of the organ, gives birth to 
all the tones of a song: if the tune is to be changed, the 
cylinder must be pulled out or pushed in one or more 
notches, to present other notes to the keys. In the same 
manner let us suppose that nature has impressed or en- 
graved certain determinations or notes of action, fixed in 
a determinate series in the nervous system and the gan- 
glions of the caterpillar, by which alone she lives, she 
will act according to a certain sequence of operations; 
and, so to speak, she will sing the air engraven within her. 
When she undergoes her metamorphosis into a butterfly, 
her nervous system being, if I may so express myself, 
pulled out a notch, like the cylinder, will present the 
notes of another tune, another series of instinctive ope- 
