Romanes finds in the Arthropoda evidences not only of intelligence,
but also (in the Crustacea) of reasoning. Bethe, on the other hand,
denies that either associative memory or consciousness exists in any of
the Arthropoda (Crabs, Spiders, Insects, etc.) The admittedly complex
behavior of these forms is ascribed by Bethe entirely to “reflex
action,” wholly devoid of psychic elements.
“This opinion,” says Holmes, “is in part based on _a priori_ deductions
from the organization of the nervous system and it is held to
chiefly by morphologists and physiologists whose observation of the
behavior of animals is limited and warped by preconceptions.” Bethe’s
experiments were “obviously inadequate.” As Loeb facetiously puts it,
“his conclusions are based upon a few spankings he gave a Crab which
obdurately rushed into a dark corner (its instinctive action when
frightened) despite the presence there of a Devil-fish (Edolene), the
Crab’s natural enemy.”
Yerkes and Huggins, Cowles and other observers have found that Crabs
and Crayfish are both capable of learning by experience; while
Spaulding has demonstrated the capacity of Hermit-crabs (Pagurus
longicarpus) to form associations.