About 60 years ago Harry Schroeder performed an experiment on willow-moth
caterpillars. At pupation these caterpillars crawl onto leaves, pull the tips
over, then wrap the rest of the leaves around themselves.
Schroeder waited until the caterpillars were on the leaves before cutting the
tips of the leaves off. The caterpillars responded by using the sides instead.
Pupation continued normally thereafter.
When the time to pupate arrived for the subsequent generation 4 of the 19
offspring used the sides of the leaves in preference to the tips.
Some time ago Frederick Griffiths performed an experiment on rats whereby they
were placed on slowly revolving turntables for periods of up to 18 months or
When the rats were removed from the turntables their heads continued to flick
in the direction of rotation and so did their eyes. This automatic flickering
then appeared in their offspring.
Comment: Imagine the experiment on the caterpillars being repeated along with a
control group whose leaves were not altered: If it were found that genetic
changes only occurred in the group with tipless leaves then this would begin to
indicate that the change in behaviour wasn`t due to chance mutations.
Repeat the experiment often enough, and if the results were consistent, it
would soon be statistically impossible for random mutations to be a factor.
The second experiment, though appalling, also had a potential: If it had been
continued then grotesque structural changes similar to those found in flatfish
might have occured.
The results of both experiments are of personal interest because they would be
consistent with the existence of an internal evolutionary mechanism based on an
extension to homeostasis.
References to these experiments are to be found in "The Great Evolution
Mystery" by Gordon Rattray Taylor (Secker & Warburg, London). If any Reader
knows the location of the primary sources of these, or similar, experiments it
would be greatly appreciated.
Model of an Internal Evolutionary Mechanism (based on an extension to
Stationary Phase Mutations to The Baldwin Effect: