at birth to stimuli of a highly general instead of a defi-
nitely particularised character, and this is the first step in
the conversion of an instinct into a general tendency
capable of being directed by experience. The instinctive
tendency as such becomes more general, and experience
makes it definite.

7. Retrogressive Assimilation.

In the cases hitherto discussed, there was to begin with
a reaction, random or instinctive, to a certain stimulus, and
the effect of experience was to modify this reaction. We
pass now to cases in which a reaction is acquired to which
there is no initial tendency. In the former cases, the reaction
had to be modified; in these it has to be as it were created.

The sight of a man or the sound of a human voice
cannot under ordinary circumstances stimulate a wild
animal that does not prey upon man to expect food or
prepare to receive it. But if the same animal is caught
and kept in captivity, it will soon "get to know" its
keeper and perhaps its feeding time. If it is an intelligent
animal it may itself be readily trained to make conventional
signs of its desire for food, as I have seen an elephant ring-
ing a bell and turning a rattle, while a smaller elephant in
the next stall would knock with its trunk against the sides
of its cage to win back to itself the attention and the buns
which were being unfairly attracted by its neighbour. But
in its simpler form, this operation of experience is seen
very much lower down in the intellectual scale. Fish, for
example, which are accustomed to be fed, will come to the
surface and be ready to snap as soon as any one approaches
their tank. Mr. Bateson ¹ describes a rockling which
under these circumstance would lift its head above water
and snap at the fingers. According to Brehm ² tortoises
and turtles in general become accustomed to men who
treat them well--though it is probably the human form or
voice to which they react, as it is elsewhere said that the
most easily tameable of Chelonia do not distinguish indi-
viduals. ³ Watersnakes we learn on the same authority, ⁴
get excited when the keeper bringing food opens the door

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