40 INTRODUCTION TO ZOOLOGV. 



To those who delight in the contemplation of such pheno- 

 mena, it affords high gratification to observe from a boat, on 

 a calm night, the effulgence which these creatures shed over 

 the depths below. We have always, at such times, been re- 

 minded of the wild and beautiful lines of Coleridge: 



" Beyond the shadow of the ship 



I watched the water-snakes ; 

 They moved in tracks of shining white, 

 And when they reared, the elfish light 



Fell off in hoary flakes. 



" Within the shadow of the ship 

 I watched their rich attire: 

 Blue, glossy green, and velvet black ; 

 They coiled and swam, and every track 

 "VYas a flash of golden fire. 



" happy living things! no tongue 



Their beauty might declare : 

 A spring of love gushed from my heart, 

 And I blessed them unaware." 



Professor Kymer Jones, in speaking of the luminosity of 

 the ocean, which is principally owing to the Acalepha*, 

 remarks: "We have more than once witnessed this pheno- 

 menon in the Mediterranean, and the contemplation of it is 

 well calculated to impress the mind with a consciousness of 

 the profusion of living beings existing around us. The light 

 is not constant, but only emitted when agitation of any kind 

 disturbs the microscopic Medusa3 which crowd the surface of 

 the ocean ; a passing breeze, as it sweeps over the tranquil 

 bosom of the sea, will call from, the waves a flash of brilliancy 

 which may be traced for miles ; the wake of a ship is marked 

 by a long track of splendour ; the oars of your boat are raised 

 dripping with living diamonds ; and if a little of the water be 

 taken up in the palm of the hand, and slightly agitated, 

 luminous points are perceptibly diffused through it, which 

 emanate from innumerable little Acalephse, scarcely perceptible 

 without the assistance of a microscope. All, however, are 

 not equally minute ; the Beroes, in which the cilia would seem 

 to be most vividly phosphorescent, are of considerable size ; 

 the Cesium Veneris, as it glides rapidly along, has the ap- 

 pearance of an undulating ribbon of flame several feet in 

 length; and many of the larger Pulmonigrade forms shine 

 with such dazzling brightness, that they have been described 



