Some authors find evidences of intelligence in the Cœlenterata, which
includes Hydroids, Jelly-fish, Sea-anemones, etc. The Sea-anemone,
possessing no nerve-ganglia, when dislodged from its partnership with
the Hermit-crab will quickly attach itself to the Crab’s leg and again
climb up on to the back of the shell, in which the crustacean makes its
“home.”
Professor J. Arthur Thomson observes that the Sea-anemone “is in some
cases more than quiescent in regard to the partnership,” and adds that
while responsiveness to the touch of the Hermit-crab may have come
to be ingrained in its early constitution, “it is difficult to think
clearly of its racial establishment.”
The behavior of some Cœlenterata, as Holmes remarks, “is often highly
plastic and capable of being modified in many ways as the result of
previous experience.” This is true also of the Vermes (“worms”) and
Echinodermata. “We do not intend to deny the existence of intelligence
in the groups mentioned; we think it not improbable that intelligence
of a primitive sort may be discovered, at least in the more highly
developed members of these divisions; but at the present time we can
only grant the Scotch verdict of ‘not proven’.”[8]