ZOOPHYTES. 833 



languid, their rapid flapping being the effect of the con- 

 traction and expansion of the disk, whereby the margin is 

 moved quickly backwards and forwards, carrying the ten- 

 tacles with it. Occasionally, however, all the tentacles 

 are strongly brought together at their tips, with a twitch- 

 ing, grasping action, like that of fingers, which is certainly 

 independent of the disk, and may be connected with the 

 capture of the prey. 



Now every detail of the structure here, as well as the 

 general form, appearance, and habits, agrees with the 

 small naked-eyed Medusae, so closely that if we had not 

 witnessed the birth of the little creature from the repro- 

 ductive cell of a Laomedea, we should have pronounced it 

 with unhesitating confidence a true Acaleph. The pedun- 

 cle, it is true, seems out of place, being on the outside of 

 the dome, instead of hanging suspended from its interior ; 

 but this difference is only apparent, and arises from the 

 circumstance that the disk is reverted. If you suppose 

 the edge of the disk to be turned in the opposite direc- 

 tion, you will have the peduncle in its proper place : the 

 umbrella in these specimens is carried within, and the 

 sub-umbrella without; an inversion which is probably 

 accidental, or, at least, unimportant. 



Comparing now this strange production of a Medusa by 

 a Polype, with what I lately told you of the production of 

 Polypes by a Medusa (as in the case of the lovely little 

 Turris), you will have some acquaintance with the won- 

 drous phenomena which have of late years been surprising 

 and interesting naturalists, viz., those of the Alternation 

 of Generations ; in which, as Chamisso, the first disco- 

 verer of the strange facts, observed, " a mother is not 

 like its daughter, or its own mother, but resembles its 

 sister, its grand- daughter, and its grandmother." The 

 Polype gives birth to a generation of Medusae which lay 

 eggs, which develop into Polypes. The Medusa on the 

 other hand lays eggs (gemmules), which develop into 



