146 A NATURAL HISTORY OF THE SEAS 



contained anything larger than a sardine, and it is therefore 

 probable that the sword is used mainly to rake up sand 

 and so dislodge the small animals upon which it feeds. 



Another giant is that strange creature known as the 

 Oar or Ribbon Fish (Regale cus glesne). It has an elongate 

 form extending 20 feet, and its shape combined with the 

 long filamentous spines on the pelvic fins and curiously- 

 shaped head have no doubt done much to make the fish 

 popularly accepted as a sea-serpent. Nothing is known 

 of its eggs, early stages or habits. 



The chameleon has from time immemorial been popu- 

 larly accepted as the quick-change artist par excellence of the 

 animal world. Actually its power of changing colour 

 at short notice is easily eclipsed by many other animals, 

 notably fishes. Though the remarkable colour changes in 

 fishes have been noted from early times, their actual 

 significance has been appreciated but recently, and we 

 are only now beginning to fully understand the manner 

 of their mechanism. 



Briefly, the colour changes are due to the presence 

 of special pigment cells in the skin, which being contracted 

 or dilated produce various effects. The actual range of 

 pigments is limited, but endless combinations can be 

 formed by the excitement or otherwise of diverse cells 

 in close proximity to one another. Thus the vivid green 

 of the mackerel is due not to the presence of green pigment, 

 but to the juxtaposition of black and yellow pigment 

 cells which operate with varying degrees of intensity. 



Recent researches by Professor G. H. Parker, of Harvard 

 University, have demonstrated that these colour phases 

 are brought about by a gland-like action of the nerve 



