TEE NERVOUS SYSTEM 121 



since no absolute criterion for consciousness in any organism other than 

 one's self can be given. Earthworms, however, apparently possess some 

 capacity to profit by experience. Within the past year Yerkes has re- 

 ported on the training of an earthworm which in a surprisingly short 

 time acquired the habit of escaping successfully from a very simple maze. 

 These results, should they prove true for other individuals, suggest a 

 certain degree of consciousness in these creatures as a basis of their 

 ability to learn. It is, therefore, not impossible that certain of the 

 reflexes of earthworms may be associated with conscious states, even 

 though these states may be of a very low order. 



But, though the reflexes of the lower animals show some features 

 that suggest consciousness, it is not probable that this state is anything 

 like as characteristic of these simple forms as of the more complex ones. 

 Certainly some of the performances of these more primitive beings 

 have every mark of the unconscious reflexes of our own bodies. Thus 

 bees that have been artificially hatched and have never seen the colony 

 at work make as perfect comb as though they had learned the art by 

 having been co-workers in an established hive. Such bees, moreover, 

 will not only build comb such as they themselves were hatched from, 

 but will shape a queen cell, a form with which they have had absolutely 

 not the least acquaintance in the past. Thus the very complex opera- 

 tion of comb-building in the bee resembles our own unconscious inborn 

 reflexes, such as the constriction of the pupil and the movements of the 

 digestive tube, rather than our voluntary operations, and this is probably 

 true of many of the activities of the lower animals. In fact, it seems 

 fair to conclude that, though such animals as the insects, crabs, and 

 even the worms, possess a nervous system composed of elements similar 

 to those in the higher forms, their reflexes are much more mechanical 

 and less associated with anything that can be called a conscious state 

 than are those of the higher forms. In other words, these lower animals 

 are more in the nature of reflex machines than are the higher form3, 

 though they are not, as some investigators would have us believe, ex- 

 clusively so. 



But if the nervous system in many of the lower animals is com- 

 posed of elements similar to those in the higher forms, and exhibits 

 activities not unlike our own, are there not still more primitive animals 

 in which this system shows a real reduction and exhibits a condition 

 which marks the actual beginnings of nervous organization? Such 

 primitive forms have long been supposed to exist among the ccelenter- 

 ates and are well represented by the sea-anemones. 



Sea-anemones are sack-like animals with a single opening leading 

 into the digestive cavity and serving both as mouth and anus. This 

 opening is usually surrounded by a cluster of tentacles. The living 

 body of the sea-anemone consists of the thin membranous wall that 



VOL. LXXXIV. — 9. 



