BEHAVIOUR OF SHORE ANIMALS 241 



SOME CHARACTERISTIC ACTIVITIES OF SHORE FORMS FROM 

 THE STANDPOINT OF BEHAVIOUR 



Certain characteristic activities of shore forms to which 

 we have referred already in other connections deserve 

 further study from the standpoint of behaviour. They 

 are : the construction of tubes by Polychaets, and similar 

 activities ; the occupation of molluscan shells by hermit 

 crabs ; and the masking of spider crabs. 



Tube-building in Polychsets. — Many marine worms are 

 adapted to living in tubes of their own construction. Most 

 frequently, the tubes are formed of particles of sand, mud, 

 or similar material collected by the tentacles and cemented 

 in position by a substance secreted by the body. The 

 accuracy with which these particles are fitted and the 

 symmetrical and finished appearance of the tubes are 

 often extraordinarily fine. What is equally wonderful 

 is that out of a heterogeneous mass of material at the 

 disposal of the worm only fragments of one particular 

 kind are selected and employed. What interpretation is 

 to be placed upon the behaviour is, in the absence of careful 

 experiments, not apparent. The tendency is, perhaps, 

 without sufficient evidence, to postulate intelligence. Thus, a 

 case of what is described as " apparent intelligence " has 

 been observed in Terehella conchilega (Watson, 19 16). 

 One of these worms, with the combined efll^ort of several 

 tentacles, was observed to be lifting to the edge of its tube 

 a piece of gravel too large to enter the opening. It appeared 

 to the observer that the stone was too large, and that when 

 placed on the edge of the tube it must necessarily fall ofi^, as 

 the cement supplied by the animal's lips would be too weak 

 to hold it in position. However, the stone in due time reached 

 the edge of the tube, held by several tentacles ; the worm 

 then emerged to receive it and with its lips grasped as much 

 of the stone as they would cover, and then rested it upon 

 the edge of the tube. The observer then expected to see 

 it fall, but it was kept in place by the tentacles which were 

 now passed around it. A supply of small grains of sand 



