70 THE ESSEX NATURALIST.
the case of useful plants, the transition from Exploitation to
Enslavement is a natural and normal process. The first con-
sequence of Exploitation is diminution of local supply and the
need of the collector to go farther afield for what is required to
meet the demands of Human Society. In time the cost of
transport of the product concerned exceeds the price the product
will fetch, or, if the product be regarded by Human Society as
indispensable, the risk of exhaustion of supplies has to be faced.
The interests of the generation concerned in such cases automati-
cally, if unconsciously, safeguards the rights of posterity by
reducing the source of the product to captivity and cultivating
it under plantation conditions. A typical instance of this
sequence of events was considered by us two years ago in the
transfer of the wild Cinchonas of the Andes to plantations in
India, Ceylon and Java. Earlier examples of the same kind
are provided by Coffee and Tea. Within the memory of some
of us the same thing has happened to the rubber-yielding Hevea
of Brazil, now an important plantation crop in the British and
the Netherlands Indies; within the memory of all here this has
occurred to a fibre-yielding Agave of Mexico, now the important
Sisal crop of East Africa. In all these cases we observe that
though the plants are now cultivated, they are still as truly
exploited as the pheasant is among game-birds; and, like the
pheasant, show that the treatment of animals or plants hunted
in the field only differs in degree from that of animals or plants
exploited in captivity. The few cases in which Man has estab-
lished economic contact with insects illustrate the same transition
from Exploitation to Enslavement. The Coccus that once
supplied lac-dye, and still yields the resin that provides Human
Society with sealing-wax and gramophone records, is a good
example of an organism actively exploited. In this case Man
only conserves and protects the groves and thickets in which
the insect settles spontaneously. The case was different with
that other Coccus which once yielded cochineal-dye: there Man
made captivity a prelude to exploitation, and formed Nopalries
in which the insect could be reared and fed till it was ripe for
destruction. This victim of human cupidity has had its revenge
in the trouble and expense incurred by Human Society in
eradicating the Nopals that made its exploitation possible. Men
learned long ago from the bear that the honey-bee was worth