THE EMERGENCE OF VISION 107 



maintained by electrical oscillations, have been constructed so that they can 

 explore their environment with an apparent purpose. A photo-cell can serve 

 as a receptor and amplifiers and motors can be interconnected in such a way 

 that a positive taxis (for example) to a moderate light and a negative taxis to 

 bright light (or to material obstacles, gradients, etc.) can endow it with the faculty 

 to discriminate between effective and ineffective behaviour, to seek actively an 

 environment with moderate and optimal conditions, to acquire conditioned 

 reflexes, and even to perpetuate its activity and " feed " itself with electricity 

 by being optically attracted to a charging circuit when its batteries begin to fail. 



On the other hand, there are those who consider that such auto- 

 mata have httle resemblance to even the simplest living things ; their 

 behaviour has only a superficial appearance of being dominated by- 

 taxes and kineses, by memory, habituation or trial-and-error learning. 

 The school of biological philosophy formalized by Whitehead (1929), 

 amplified by McDougall (1933) and pursued by such recent writers as 

 Agar (1943) and Thorpe (1956) argues that every vital event is an act 

 of percejition. a mental as opposed to a material process ; a living 

 organism is essentially something which perceives ; its behaviour 

 is not an automatic response to sensory impressions but includes an 

 element of purpose building up primary perceptions into unitary 

 systems in which the whole is different from and greater than the 

 sum of its constituent parts. Such a view, as we have already hinted, 

 tends to pan-psychism, or even to pan-theism ; according to it a 

 purely objective biology is sterile ; like the warp and woof, mechanism 

 must be interwoven with teleology.^ While mechanisms may even- 

 tually become explicable in physico-mathematical terms, there is no 

 suggestion yet that the subjective concepts of conscious purpose ever 

 will be (Sommerhoff, 1950). But. even although this is agreed, it is to 

 be remembered that there are no grounds for supposing that any 

 well-defined mental content is associated with the reactions of the 

 lower animals comparable to the perceptual experiences of the 

 higher animals. 



On tlie whole it would seem that the matter is not so simple as the 

 more materialistic outlook might suggest. It is true that many of these 

 primitive tropic activities of the animal world can be interpreted as 

 reflexes without motivation, incentive or appreciation ; but because 

 there are no discernible conscious acconipaniments to many purely 

 reflex acts in man whose apperceptive powers have been translated 

 from the level of ganglia to the cerebral cortex, it by no means follows 

 that there are none in those lowlier organisms the nervous system of 

 which consists only of ganglia and nerve -fibres — or even of an un- 

 centralized nerve-net or nothing at all. It must be remembered that the 

 transference of sensory appreciation to the neopallium occurred late in 

 evolutionary history,^ and that although the lower centres in man have 



1 See D'Arcy Thompson (1942). = p. 542. 



