50
M. J. WELLS
adopt characteristic postures with the column bent in ways that
remain constant over considerable periods of time. When an individual
contracts and re-expands, it returns to a shape that it held before the
contraction, often a shape that happens to fit the available space in its
own immediate surroundings; one is reminded of Teyrovsky’s (1922)
experiments with tube-worms. In the case of the anemones, however,
there is no need to postulate habit formation, for it seems that the
essential elements of the individual’s characteristic shape are retained
as local differences in muscle tone even when it is largely contracted.
After any maximal contraction, the “ habit ’’ is lost. Animals can be
“ trained ” to adopt a new position by any form of punishment that
eliminates this “ muscular memory ’’ (Jennings, 1905). Anemones
placed in aquaria are said to select the under or upper sides of surfaces
depending on the site from which they were collected. If true, this
position habit could be interpreted as associative memory (Thorpe,
1963). The experimental evidence is, however, unconvincing because
the numbers of animals involved have always been small and because
lighting effects, which are known to be important, have not always
been adequately controlled. The most complete account is by Ghinst
(1906) who did a series of experiments with Actinia epuina placed
upright or upside down between two horizontal glass sheets. Ghinst,
who did his experiments in a darkroom, recorded how long the animals
took to attach and whether they ended up facing upwards or downwards. He was able to conclude only that the “ position memory ”
accelerated or retarded attachment, depending on whether their new
position was the same or different from their position when collected.
Much more recently Ross (1965) has reported two further experiments that appear to show conditioning in sea anemones. I n the first of
these, an attempt was made to link the mouth opening of Netridiurn
with low frequency electric shocks. The unconditioned stimulus wm
squid-juice, applied while the anemone was receiving small electric
shocks (condenser discharges) at intervals of several seconds. Shocks
separated by more than 3 sec normally have no effect. Forty-five
anemones were trained. Twenty-seven of these had to be discarded in
the course of the experiment because they ceased to respond to the
squid or covered the mouth with the tentacles. Of the rest, seven
began opening the mouth wide in response to shocks alone after ten to
twenty trials, three made smaller responses of a similar kind and
eight showed no changes in behaviour. In a repeat series no positive
results were obtained at all.
More promising perhaps are experiments recently begun with
Stomphia, which responds in a remarkable way by expanding, detach-
M. J. WELLS
adopt characteristic postures with the column bent in ways that
remain constant over considerable periods of time. When an individual
contracts and re-expands, it returns to a shape that it held before the
contraction, often a shape that happens to fit the available space in its
own immediate surroundings; one is reminded of Teyrovsky’s (1922)
experiments with tube-worms. In the case of the anemones, however,
there is no need to postulate habit formation, for it seems that the
essential elements of the individual’s characteristic shape are retained
as local differences in muscle tone even when it is largely contracted.
After any maximal contraction, the “ habit ’’ is lost. Animals can be
“ trained ” to adopt a new position by any form of punishment that
eliminates this “ muscular memory ’’ (Jennings, 1905). Anemones
placed in aquaria are said to select the under or upper sides of surfaces
depending on the site from which they were collected. If true, this
position habit could be interpreted as associative memory (Thorpe,
1963). The experimental evidence is, however, unconvincing because
the numbers of animals involved have always been small and because
lighting effects, which are known to be important, have not always
been adequately controlled. The most complete account is by Ghinst
(1906) who did a series of experiments with Actinia epuina placed
upright or upside down between two horizontal glass sheets. Ghinst,
who did his experiments in a darkroom, recorded how long the animals
took to attach and whether they ended up facing upwards or downwards. He was able to conclude only that the “ position memory ”
accelerated or retarded attachment, depending on whether their new
position was the same or different from their position when collected.
Much more recently Ross (1965) has reported two further experiments that appear to show conditioning in sea anemones. I n the first of
these, an attempt was made to link the mouth opening of Netridiurn
with low frequency electric shocks. The unconditioned stimulus wm
squid-juice, applied while the anemone was receiving small electric
shocks (condenser discharges) at intervals of several seconds. Shocks
separated by more than 3 sec normally have no effect. Forty-five
anemones were trained. Twenty-seven of these had to be discarded in
the course of the experiment because they ceased to respond to the
squid or covered the mouth with the tentacles. Of the rest, seven
began opening the mouth wide in response to shocks alone after ten to
twenty trials, three made smaller responses of a similar kind and
eight showed no changes in behaviour. In a repeat series no positive
results were obtained at all.
More promising perhaps are experiments recently begun with
Stomphia, which responds in a remarkable way by expanding, detach-