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 
light, 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 . 1 
1 See Croonian Lecture, 1881, in forthcoming issue of Phil. Trans. 
