452 THE ZOOLOGIST. 



later. A Sea- Urchin of 27 mm. was given a pebble which it 

 carried, not quite as far as, but nearly to, the anus, where it 

 was retained, in twelve minutes. The other individual of 27 mm. 

 carried a pebble given to it for about half the distance between 

 its periphery and its anus, where the stone was. held, and no 

 further progress was made during the following half hour. A 

 Sea-Urchin of 23 mm. carried a pebble from the periphery to 

 the anus in fifteen minutes. Flattish stones of about 5 mm. were 

 used in the experiments. The foregoing observations seem to 

 me to suggest that, if it is going to carry the objects at all, the 

 Sea-Urchin deliberately directs them towards its anal region. 



The chief facts recorded in this paper, and the inferences 

 which may, I think, be fairly drawn from them, can be sum- 

 marized as follows : — 1. The proportion between weight of 

 objects and weight of body is greater in the smaller than in the 

 larger Sea-Urchins. 2. Objects are more frequently picked up 

 by the smaller animals. 3. The smaller ones substitute objects 

 for those which have been removed from them more certainly, 

 quickly, and determinedly than do the larger ones. 4. The 

 habit of carrying numerous objects is probably lost with age, 

 but that of covering the anus is retained. 5. The objects are 

 usually arranged so as to cover the anus, even if the other parts 

 are left exposed. 6. The probable uses of the objects over the 

 anus are : (a) to hide the eye-like anal region ; (b) to confuse an 

 enemy as to the place from whence the fasces issue ; (c) to keep 

 off the stomachs of Starfishes. 7. Objects picked up are usually 

 transferred to the anus. 



It formerly seemed to me to have been too readily assumed 

 that foreign objects were picked up and carried by the Sea- 

 Urchin for purposes of disguise. Some of the objects (such as 

 living molluscs) even seemed likely to attract carnivores which 

 might attack the Sea-Urchin itself, whilst others (such as one 

 tiny pebble on a large individual) seemed to be entirely useless. 

 Again, the peculiar locomotory organs of the Sea-Urchin had to 

 be taken into account. These and other considerations raised 

 the question whether the Sea-Urchin really possesses an instinct 

 which prompts it to pick up materials which will act as a 

 disguise, or whether the animal in creeping along, or in climbing, 

 or in steadying itself, affixes some of its tube-feet to loose neigh- 



