118 SOME WONDERS OF THE SEA. 



in the same direction, little waves of opalescent light arc 

 seen to ripple, as beautiful and as changeable as the 

 colours of a soap-bubble. 



On account of the regularity of these colour-waves, 

 the creatures were at one time called Fountain Fishes, 

 the always changing hues being attributed to little streams 

 of coloured liquid perpetually being ejected. 



The creature is perpetually on the move, turning over 

 and over, falling and rising, and proceeding in a series 

 of graceful curves. Trailing from it there will soon 

 appear two long, very slender filaments. These threads 

 are of extreme delicacy, but on examining them a little 

 more closely, each thread will be seen to have a row of 

 filaments, comparatively short, but of still greater tenuity, 

 attached to it throughout its whole length. These are 

 the " fishing-threads," and the Cydippe Avill be seen to 

 extend and contract the whole thread system at will, 

 so that it is not of the same length for two consecutive 

 seconds. 



If several specimens be placed in the same vessel, they 

 swim about quite freely, and it is a curious fact that 

 although the trailing threads often come in contact with 

 each other, they are never entangled, and in spite of 

 their tenuity are not broken. 



Through the transparent tissues the digestive organs 

 are visible, but the most interesting portion of the 

 structure is the mechanism by which the creature moves, 

 and from which the rippling light-waves take their 

 origin. With a little ingenuity it is always possible to 



