HYDRA TUBA. 213 



one's attention. It far excels the wildest dreams of 

 fiction ; and were it not so well authenticated by 

 naturalists who have devoted labour and valuable time 

 to gain ocular demonstration of the fact, we might 

 well hesitate to believe the statements laid before us 

 in their works. 



For example, a Polype, as Hydra Gelatinosa or 

 Hydra Tuba (found on buoys, oyster shells, &c., long 

 submerged), will, it may be in a simple aquarium, 

 produce a number of small objects which, on being 

 examined through the microscope, are found to be, 

 not young Polypes, but Jelly-fish ! In process 

 of time, the latter, by a wondrous law of nature, 

 will produce in their turn, not Medusae, but 

 Polypes ! 



' Imagine/ says Mr. Lewes, ' a lily producing a 

 butterfly, and the butterfly in turn producing a lily, 

 and you would scarcely invent a marvel greater than 

 this production of Medusae was to its first discoverers. 

 Nay, the marvel most go further still, the lily must 

 first produce a whole bed of lilies like its own fair 

 self before giving birth to the butterfly, and this 

 butterfly must separate itself into a crowd of butter- 

 flies, before giving birth to the lily.' 



Let me now, by entering briefly into detail, 

 endeavour to make the reader acquainted with the 

 leading features of this mysterious subject, known as 

 ' the alternation of generations/ 



The adult Medusae, then, gives birth to a number 



