JELLY FISH'S POISONOUS STIXG. 101 



from one to ten globular objects. Some observers say 

 that these objects vibrate, while others have failed to 

 detect the slightest movement. It has been conjectured, 

 and in fact asserted, that the tiny objects within these 

 vesicles are analogous to the ear-bones or " otoliths " of 

 fishes, and so the sacs have been called " otolithic vesi- 

 cles," and their function assumed to be connected with 

 the sense of hearing. But I cannot accept these vesicles, 

 irregular in number and variable in contents, as having 

 any analogy to the ear structure of the higher animals, 

 and am sure that their real office is yet to be discovered. 



A few words about the development of the Medusae 

 must terminate this portion of the Jelly Fish's life-history. 



The Medusa which we find lying on the sea-shore has 

 not always possessed the same shape. It has not merely 

 grown from a little Jelly Fish into a large one, any more 

 than a house fly grows into a bluebottle, or a gnat into 

 a daddy-longlegs. 



It has passed through a series of changes before it has 

 assumed the form in which we know it; but all indi- 

 viduals need not undergo the same changes. If we trace 

 the creature through its previous existences, and suppose 

 it to go through all of them, we first find it in the state 

 of an egg. Thence issues an embryo covered with cilia, 

 or hair fringes, by the movements of which it swims 

 rapidly through the water. Then it settles down for its 

 next change, affixes itself to a seaweed o r similar object 

 and becomes a bell-shaped animal, fixed by the base to 

 the seaweed, and having long tentacles projecting from 



