SECT. III. 



NAKED-EYED MEDUSA. 



93 



of the stomach into the four radiating canals, to supply 

 the waste and nourish the system. The digestive cavity 

 and canals are lined with a soft membrane, covered with 

 cilia, whose vibrations maintain the circulation of the 

 juices and perform the duty of a heart; for the medusae 

 have none, nor have they any special respiratory system : 

 their juices are aerated through the under-surface of the 

 rim of the umbrella, while passing through the circular 

 canal lying either within the water or on its surface. 



A fringe of filamental tentacles hangs down into the 

 water from the rim of the disc or umbrella, which is 

 studded at equal distances by fleshy bulbs, each of which 

 has a group of fifty dark eye-specks, being the rudiment 

 of an eye ; and if the animal be disturbed when in the 

 dark, each eye-speck shines with a brilliant phosphoric 

 light, and the umbrella looks as if it were begirt with 

 a garland of stars. 



Close to the edge of the canal which encircles the 



Fig. 113. Otclites of Magnified Thaumantias. 



margin of the umbrella, there are eight hollow semi- 

 oval enlargements of the flesh, two in each quadrant 

 formed by the four radiating canals : they are the eight 

 ears of the medusa, for in these hollow organs there are 

 from thirty to fifty solid, transparent, and highly refrac- 

 tive spheres, arranged in a double row, so as to form a 

 crescent, those near its centre being larger than the 

 more remote. The solid spheres are analogous to the 

 otolites in the ears of the more highly organized animals. 



