20 REPRODUCTION OF VORTICELL^E. 



gradual widening of the bell, which then assumes a globular 

 shape, and next that of a flattened sphere ; at which stage of 

 the process a band-like constriction makes its appearance in the 

 middle, and gradually increasing in depth, it at length separates 

 the original animal into two, both of which still remain attached 

 to the stalk. But as only one of the two is to remain in pos- 

 session of this piece of joint-property, the subsequent develop- 

 ment of the two animals is singularly dissimilar. In the one 

 which is to retain possession of the original stalk, the upper 

 extremity opens out into the regular bell-mouth form, around 

 which the fringe of cilia are speedily seen in active motion : in 

 the other, on the contrary, the upper extremity still remains 

 closed, and the cilia are developed at the lower extremity near 

 the junction with the stalk, from which the young Vorticella 

 now speedily shoots away, a free, swimming animalcule. Its 

 roving life, however, is soon over ; for looking out a convenient 

 spot for its future home, it speedily settles down, and attaching 

 itself by what was at first the upper part of its body, it 

 gradually rises on a stalk of its own, and in due time becomes a 

 fully developed Bell Animalcule. 



Another curious mode of reproduction amongst the Vorticella?, 

 as amongst some other tribes of these minute organisms, is by 

 what is known as the encysting process. In this mode of 

 obeying the injunction to " increase and multiply," the Vorti- 

 cella withdraws the ciliated margin of the bell, and contracting 

 itself into a cyst or purse, secretes a gelatinous covering, whicli 

 gradually solidifies, and forms a sort of capsule within which the 

 animal is completely enclosed. In this state it remains for some 

 time, it may be only a few hoxirs or it may be clays, in the course 

 of which the substance of the original animal becomes broken 

 up, so to speak, into a number of minute oval bodies which 

 move about with great activity within the transparent cyst. 

 At length some portion of the cyst Avail gives way, and the im- 

 bedded embryos suddenly shoot out into the water, where they 

 become diffused, and give rise to a new generation of Vorticellte. 



She power of enclosing themselves in a cyst is sometimes em- 

 ployed by the Vorticella; for the purpose of self-preservation, 

 when the water in which they have been residing dries up. In 

 such cases the enclosed animals are preserved from injury till the 

 falling rain again fills the pool, and calls them back to active life : 



