SENSES AND NERVES 



133 



train, but you can see and hear the effect ot tlie impulse 

 as it runs from one end to the other. 



In the sea-anemone impulses received from the sensory 

 cells in the skin are passed to other parts of the body by the 

 nerve network in this manner, and the animal responds to 

 different stimuli although the sensory cells are not clumped 

 into end organs specially adapted to pick up specific stimuli. 

 In some of the sea-anemone's near relations such as the 

 jelly-fish, however, there is greater specialization. Amelia is 

 a small jelly-fish less than a foot across that is common 

 round British coasts in the summer; it is practically trans- 

 parent and apart from four purplish horseshoe-shaped roes 

 is not adorned with the brilliant colours that make some of 

 the larger jelly-fish so beautiful. Eight equally spaced notches 

 round the edge of the disc or umbrella mark the position 



Fig. 2. The jelly-fish Aurelia. The edge of the umbrella bears numerous short 

 tentacles. The four horseshoe-shaped roes are seen through the semi-transparent 

 body and two of the four long "arms" surrounding the mouth project beyond 

 the edge. Some of the eight equally spaced notches round the edge of the um- 

 brella are seen ; they mark the position of the sense organs. 



of the sense organs, which consist of eye-spots, other cells that 

 respond to smells or tastes, and small pockets of limey 



