638 LIFE : OUTLINES OF GENERAL BIOLOGY 



and (2) that animal behaviour is either predominantly reactive (on 

 the lower side) or predominantly initiative (on the upper side). In 

 other words, the Ixhaviour may be in the main an expression of 

 what is hereditarily enregistered, or in the main an expression of 

 new tentatives and experiments. 



A corollary that the diagram also expresses is the more and more 

 manifest emergence of the mental aspect as we ascend the series. 

 This is expressed by a thickening of the dotted line on the main 

 stem, which is to be thought of as the general stream of life both 

 ontogenetic and phylogenetic. Primarily the axis of our "feather" 

 indicates the phylctic line of organismal advance from Protozoon 

 to pol>T), from polyp to worm, from worm to Arthropod and to 

 Vertebrate; it being always clearly understood that the higher 

 animals, such as horse and dog (and indeed man also) have reflexes, 

 tropisms, and instincts as well as a predominance of intelligent 

 behaviour. But without any confusion of thought the axis of our 

 feather may also represent the individual development, from embryo 

 to newborn creature, and thence through youth onwards. Again ob- 

 viously, although there is a stage when only reflexes are discernible, 

 these are not displaced when intelligence tn^gins to assert itself. 



Conveniently, moreover, the alteration in the thickness of the 

 dotted line on the branches might also indicate, did we know enough, 

 the waxing of the psychical aspect in initiative, tentative, or experi- 

 mental behaviour, and its waning in behaviour that is the outcome 

 of enregistration or the engraining of reactions. Thus we might 

 indicate part of the branching enlarged to show this alteration. 



Before summing up, we must emphasise the point that the survey 

 we have taken is concerned only with that part of the psychic life 

 of animals that may be thought of as directly underlying particular 

 doings. But that is far from exhausting the mental possibihties; for 

 even thus there is the store of sense-impressions, the accumulation 

 of experience, the ebb and flow of feeling — sometimes rising into 

 emotions, such as affection and anger. Account must be taken of 

 each of these, for the enjoyment that many animals seem to display 

 is a fact of observation, not merely at flrst sight to the unsophisti- 

 cated field-naturalist, but after the critical scrutiny of veteran 

 experts in comparative psychology. Thus "enjoyment" is to Lloyd 

 Morgan one of the criteria indicative of the pervasive psychical 

 aspect of animal Ix'haviour, and as distinctive as controlling guid- 

 ance, often with its hints of inference. 



Another inquiry that should be attempted is the grouping of the 

 springs of behaviour — the internal stimuli that lead to actions. On 

 the physiological side they are states of dissatisfaction, restlessnesses, 

 appetites, and so on; on the psychological side they are impulses, 

 desires, purjwses, and the like. The problem is to find an orderly 

 grouping. 



