500 'Journal of Comparative Neurology and Psychology. 



Evolution depends upon those organisms being selected which 

 have that certain kind of memory which enables them to cope with 

 the conditions of their surroundings. Whether this memory is 

 evolved through the inheriting of acquired aptitudes or through the 

 selection of the best adapted variants, or mutations, does not bear 

 on the question. With such factors given, and they are universally 

 accepted laws in biology, the evolution of an adaptive behavior 

 follows of necessity. It is probable that an explanation in these 

 terms seems inadequate only because of the scarcity of empirical 

 data. Observation of the physiological economy and gross behav- 

 ior of animals is the basis for such a theory of the genesis of adap- 

 tive behavior, but the only starting point for a study of conscious- 

 ness is the consciousness of the observer. 



The observer, how^ever, finds that other organisms of his own 

 species have solved problems relating to, and have systematized, 

 this very matter of consciousness, and other matters, which he, 

 though possessing consciousness, might hardly have done. This 

 at first seems one of his strongest grounds for assuming conscious- 

 ness in his fellows. But by such an assumption he implies that 

 consciousness is an aid to this solving and systematizing and that he 

 without it, could not solve and systematize. This assumption 

 he can make only by a denial of parallelism, for if consciousness 

 in him has an invariable physiological accompaniment it may then 

 be only the indicator of his ability and not an aid to this ability 

 at all. 



But if the individual wishes, for convenience or any other reason, 

 to assume consciousness in his own species, he may next consider 

 what grounds he has for attributing it to other species. It is 

 obvious that the probability of the other species possessing con- 

 sciousness is directly proportional to the similarity of their behav- 

 ior to that of the species assumed to possess it. In so far as inves- 

 tigation follows this line it is valid. 



As the behavior of any species most nearly approximates that 

 of the species next to it in the scale of genesis any speculation as 

 to the origin of consciousness may best be made by studying the 

 species in inverse order of their development. The question then 

 presents itself, does consciousness belong to every order of life .^ 

 If not, what is the lowest order that possesses it .^ 



Many criteria of consciousness have been suggested by the 

 various writers in this field, and their motives and the value of 



