12/2 DESIGN FOR A BRAIN 



Such an arrangement would be shown by any organism that 

 reacted to its environment by several independent reactions. In 

 such an arrangement each system, still assumed to be ultrastable, 

 can change its own step-functions and find its own terminal field 

 without effect on what is happening in the others. We shall say 

 that the whole consists of iterated ultrastable systems. 



Since each system is ultrastable it can adapt and learn inde- 

 pendently of the others. That such independent, localised learn- 

 ing can occur within one animal was shown by Parker in the 

 following experiment : 



4 If a sea-anemone is fed from one side of its mouth, it will 

 take in, by means of the tentacles on that side, one fragment 

 of food after another. If now bits of food be alternated with 

 bits of filter paper soaked in meat juice, the two materials 

 will be accepted indiscriminately for some eight or ten trials, 

 after which only the meat will be taken and the filter paper 

 will be discharged into the sea water without being brought 

 to the mouth. If, after having developed this state of affairs 

 on one side of the mouth, the experiment is now transferred 

 to the opposite side, both the filter paper and the meat will 

 again be taken in till this side has also been brought to a state 

 of discriminating.' 



12/2. If we start a set of iterated ultrastable systems, and 

 observe the set's behaviour, noting particularly at each moment 

 how many of the systems have arrived at a terminal field, we 

 shall find that the set, regarded as a whole, shows the following 

 properties. 



The proportion which is adapted is no longer restricted to the 

 two values ' all ' or ' none '. In fact, if the systems are many, 

 the degrees of adaptation which the whole can show will be as 

 many. A whole which consists of iterated systems will therefore 

 show in its adaptation a gradation which was seen (S. 11/2) to 

 be lacking in the fully-connected ultrastable system. 



A second property is that when one system has arrived at a 

 terminal field, the changes of the other systems will not cause the 

 loss of the first field. In other words, while the later adaptations 

 are being found, the earlier are conserved. A whole which con- 

 sists of iterated systems will therefore show some conservation of 

 adaptations. 



A third property is that, as time passes, the number of systems 



140 



