CHAP. IV Shifts for a Living 63 



parts of the body, and particularly long plume-like pieces 

 are fixed on the head." Thus, as Carus Sterne says, is the 

 story of " Birnam's walking wood " re-enacted on the sea- 

 shore. Furthermore, a Stetiorhynchus which has been 

 cleaned will immediately begin to clothe itself again, with 

 the same care and precision as before. Mr. Robertson of 

 Millport often saw Stenprhynchus lojtgirostru—a. common 

 crab — picking about its limbs and conveying the produce 

 to its mouth. " If other observations confirm the view that 

 this animal is a true vegetarian, we shall have one example 

 at least of an independent agriculturist, who is not only 

 superior of his lands, but carries them with him when 

 he removes." I also have seen the crab doing what " the 

 naturahst of Cumbrae " observed. In further illustration 

 of masking we may cite Dromia vulgaris, often covered 

 with sponge ; Dromia excavaia, with compound ascidians ; 

 the Amphipod Atyltis, with seaweed ; while a species of 

 Dorippe is said to bear a bivalve shell, or even a leaf, as a 

 shield, and another crab cuts off the tunic of a sea-squirt 

 and hitches it on his own shoulders. 



Sometimes this masking serves as a warning or deterrent ; 

 witness that hermit-crab {Pagurus cuanensis) whose stolen 

 shell is surrounded by a bright orange sponge (Suberites 

 domuncula). As this sponge is full of flinty needles, has a 

 strong odour and a disagreeable taste, we do not wonder 

 that Mr. Garstang finds that fish dislike it intensely, nor 

 can we doubt that the hermit-crab trades on the reputation of 

 its associate. In other cases the masking will aid in con- 

 cealment and favour attack. To the associations of crabs 

 and sea-anemones we shall afterwards refer. 



II. Comhination of Advantageous Qualities. — Mr. 

 Poulton describes, in illustration of the combination of 

 many methods of defence, the case of the larva of the 

 puss moth (Cerura vinuld). It resembles the leaves of the 

 poplar and willow on which it lives. When disturbed it 

 assumes a terrifying attitude, mimetic of a Vertebrate 

 appearance ! The effect is heightened by the protrusion of 

 two pink whips from the terminal prongs of the body, and 

 finally the creature defends itself by squirting formic acid. 



