Life is motion. Wallace Stevens
Today, whilst browsing the shelves of Glasgow University library I came across The Human Brain, A Guided Tour, by the eminent English neuroscientist Susan A. Greenfield.
Opening it purely at random, I came across this, on page thirty-four:
Although plants can move in the sense that they may turn to the light, they cannot generate movements as we do. Outside the realm of science fiction, no plant locomotes from one place to another. In clear contrast, all animals are on the move - that is, they are animated. Interestingly enough, the Latin animus means ‘consciousness’… The importance for moving creatures of having some kind of brain is best illustrated by an observation initially made by the late Emperor Hirohito of Japan, for whom the study of marine life was a passionate hobby. The tunicate in question is known as a sea squirt. When it is an immature larva the sea squirt spends its time swimming around: not only is it capable of coordinated movement but it also has a primitive vibration-sensitive device, crudely comparable with an ear, and a primitive light-sensitive device, roughly analogous to an eye. In fact the sea squirt could be said to have a modest brain. However, when it becomes mature the sea squirt changes its lifestyle and attaches to a rock. It no longer has to swim around anymore, because it now lives by filtering seawater. At this stage the sea squirt actually performs the remarkable act of consuming its own brain.
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