ZOOPHYTES 37-7- 



side 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 

 direction, you will have the peduncle in its normal place: 

 the umbrella in these specimens is carried within, and the 

 sub- umbrella without; an inversion which is probably 

 accidental. 



Comparing now this strange production of a Medusa 

 by a Polype, with what I lately told you of the produc- 

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

 little Turris), you will have some acquaintance with the 

 wondrous phenomena which have of late years been sur- 

 prising and interesting naturalists; viz., those of the Al- 

 ternation of Generations; in which, as Chamisso, the first 

 discoverer of the strange facts, observed "a mother is 

 not like its daughter, or its own mother, but resembles 

 its sister, its granddaughter, 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 

 Polypes, which at length divide themselves into colonies 

 of Medusas. 



At first you will perhaps see nothing remarkable in 

 another object which I collected in my rock- ramble to- 

 day. A Hermit-crab in an old Natica shell; both com- 

 mon things enough. Yet look more narrowly. The 

 greater portion of the shell is not smooth, has no such 

 porcelain- like polish as the Natica usually has, but is 

 clothed with a sort of downy nap, a coarse sponginess of 

 a grayish hue, splashed with yellowish and pink tints. 

 The shell is invested with ffydr actinia. 



