I 



Mental Processes in Animals, 359 



to favourite food-stuffs buried in the earth in which it lives, 

 would seem to possess the power of outward projection in 

 a dim and possibly not very definite form. Through their 

 marginal bodies — simple auditory or visual organs — the 

 medusae may have a rudimentary form of this capacity. 

 In any case, they seem to have the power of localization. 

 Mr. Eomanes says,* "A medusa being an umbrella-shaped 

 animal, in which the whole of the surface of the handle 

 and the whole of the concave surface of the umbrella is 

 sensitive to all kinds of stimulation, if any point in the 

 last-named surface is gently touched with a camel-hair 

 brush or other soft (or hard) object, the handle or manu- 

 brium is (in the case of many species) immediately moved 

 over to that point, in order to examine or brush away the 

 foreign body." And the same author thus describes f the 

 process of discrimination in the sea-anemone : "I have 

 observed that if a sea- anemone is placed in an aquarium 

 tank, and allowed to fasten upon one side of the tank near 

 the surface of the water, and if a jet of sea-water is made 

 to play continuously and forcibly upon the anemone from 

 above, the result, of course, is that the animal becomes 

 surrounded by a turmoil of water and air-bubbles. Yet, 

 after a short time, it becomes so accustomed to this turmoil 

 that it will expand its tentacles in search of food, just as it 

 does when placed in calm water. If now one of the ex- 

 panded tentacles is gently touched with a solid body, all 

 the others close around that body in just the same way 

 as they would were they expanded in calm water. That 

 is to say, the tentacles are able to discriminate between 

 the stimulus which is supplied by the turmoil of the 

 water, and that which is supplied by their contact with 

 the solid body, and they respond to the latter stimulus 

 notwithstanding that it is of incomparably less intensity 

 than the former." 



Here, in discrimination, we reach the lowest stage of 

 mental activity. It is exceedingly difficult, however, to 

 determine how far such simple responses to stimuli are 



* "Mental Evolution in Animals," p. 82. f Ibid. p. 48. 



