ALTERNATE GENERATIONS. 243 



De as much surprised at the sight of its off- 

 spring as the Hen that has accidentally hatched 

 a Duck's egg. At the right moment this film 

 is torn open by the convulsive contractions of 

 the animal, which, thus freed from its envelope, 

 begins at once to expand. By this time the 

 little bud has assumed the form of a Medusoid 

 or Jelly-Fish disk, with its four tubes radiating 

 from the central cavity. The proboscis, so char- 

 acteristic of all Jclly-Fishes, hangs from the cen- 

 tral opening ; and the tentacles, coiled within 

 the internal cavity up to this time, now make 

 their appearance, and we have a complete little 

 Medusa growing upon the Hydroid head. Gradu- 

 ally the point by which it is attached to the 

 parent-stock narrows and becomes more and 

 more contracted, till the animal drops off and 

 swims away, a free Jelly-Fish. 



The substance of these animals seems to have 

 hardly more density or solidity than their native 

 element. I remember showing one to a friend 

 who had never seen such an animal before, and, 

 after watching its graceful motions for a moment 

 in the glass bowl where it was swimming, he 

 asked, " Is it anything more than organized 

 water ? " The question was very descriptive ; for 

 so little did it seem to differ in substance from 

 the water in which it floated that one might 

 well fancy that some irops had taken upon 



