1 84 THE GROUNDWORK OF SCIENCE

wasp sphex, which stings spiders, caterpillars, and grass-

hoppers in the spots where their nervous ganglia respectively

lie, and so paralyzes them. According to the doctrine of

" Natural Selection," either an ancestral wasp must have

accidentally stung them each in the right place, and so the

sphex of to-day- is the naturally-selected descendant of a

line of ancestors which inherited this lucky, accidental

tendency to sting different insects differently, but always

in the right spots ; or else the young of the ancestral sphex

originally fed on dead food, but the offspring of some

individuals which happened to sting their prey so as to

paralyze but not kill them, were better nourished, and thus

the habit grew.

Finally, there is the curious instinct by which an

animal, when an enemy approaches, lies quite quiescent

and apparently helpless an action often spoken of as

"shamming death." The term is unfortunate, because the

disposition of the limbs adopted by insects which thus act

is not the same as that which their limbs assume when

such insects are really dead ; while some species are, when

thus acting, less quiescent than others. The remarkable

circumstance, however, is not that a helpless insect should

assume a posture approximating to that of its own dead,

but that such a creature, instead of trying to escape,

should adopt a mode of procedure utterly hopeless, unless

the enemy's attention be thereby effectually eluded. It is

impossible that this instinct could have been gained by

minute steps, for if the quiescence, whether absolutely

complete or not, were not sufficient at once to make the

creature elude observation, its destruction would be only

the more fully insured by such ineffectual quiescence.

We have hitherto spoken only of instinct as existing

in animals, and in certain human actions necessary for

merely organic life ; but there are a variety of human

wasp sphex, which stings spiders, caterpillars, and grass-

hoppers in the spots where their nervous ganglia respectively

lie, and so paralyzes them. According to the doctrine of

" Natural Selection," either an ancestral wasp must have

accidentally stung them each in the right place, and so the

sphex of to-day- is the naturally-selected descendant of a

line of ancestors which inherited this lucky, accidental

tendency to sting different insects differently, but always

in the right spots ; or else the young of the ancestral sphex

originally fed on dead food, but the offspring of some

individuals which happened to sting their prey so as to

paralyze but not kill them, were better nourished, and thus

the habit grew.

Finally, there is the curious instinct by which an

animal, when an enemy approaches, lies quite quiescent

and apparently helpless an action often spoken of as

"shamming death." The term is unfortunate, because the

disposition of the limbs adopted by insects which thus act

is not the same as that which their limbs assume when

such insects are really dead ; while some species are, when

thus acting, less quiescent than others. The remarkable

circumstance, however, is not that a helpless insect should

assume a posture approximating to that of its own dead,

but that such a creature, instead of trying to escape,

should adopt a mode of procedure utterly hopeless, unless

the enemy's attention be thereby effectually eluded. It is

impossible that this instinct could have been gained by

minute steps, for if the quiescence, whether absolutely

complete or not, were not sufficient at once to make the

creature elude observation, its destruction would be only

the more fully insured by such ineffectual quiescence.

We have hitherto spoken only of instinct as existing

in animals, and in certain human actions necessary for

merely organic life ; but there are a variety of human