ECHINODERMATA. 23 



of the animal, depends, as in the other Medusae, from the 

 summit of the concave surface of the bell, like a clapper 

 or tongue. Now M^Crady observed this depending organ 

 to be moved first to one side and then to the other side 

 of the bell, in order to give suck to the larvae on the 

 sides of the bell — the larvae dipping their long noses into 

 the nutrient fluids which that organ of the parent's body 

 contained. I cite this case, because if it occurred in one 

 of the higher animals it would probably be called a case 

 of instinct ; but as it occurs in so low an animal as a 

 jelly-fish, it is unreasonable to suppose that intelligence 

 can ever have played any part in originating the action. 

 Therefore we may set it down as the uncompounded 

 result of natural selection. 



Some species of medusae — notably Sarsia — seek the 

 Kght, crowding into the path of a beam, and following it 

 actively if moved. They derive advantage from so doing, 

 because certain small Crustacea on which they feed like- 

 wise crowd into the light. The seeking of light by these 

 medusae is therefore doubtless of the nature of a reflex 

 action which has been developed by natural selection in 

 order to bring the animals into contact with their prey. 

 Paul Bert has found that Daphnia pulex seeks the light 

 (especially the yellow ray), and Engelmann has observed 

 the same fact with regard to certain protoplasmic organisms. 

 But in none of these or other such cases is there any 

 evidence of a psychical element being concerned in the 

 process. 



Echinodermata, 



Some of the natural movements of these animals, as 

 •also some of their movements under stimulation, are very 

 suggestive of purpose; but I have satisfied myself that 

 there is no adequate evidence of the animals being able to 

 profit by individual experience, and therefore, in accordance 

 with our canon, that there is no adequate evidence of their 

 exhibiting truly mental phenomena. On the other hand, 

 the study of reflex action in these organisms is full of 

 interest — so much so that in my next work I shall take 

 them as typical organisms in this connection.^ 



^ See Croonian Lecture, 1881, in forthcoming issue of Phil. Trans, 



