CILIATA 



779 



tions are either lost or retracted, as is well seen in Vorticella 

 (fig. 596, A). A new wreath of cilia, however, is developed near 

 the base, and in this condition the animal detaches itself from its 



FIG. 595. Fissiparous multiplication of Chilodon cucitUiilus: A, 

 B, C, successive stages of longitudinal fission (?) ; D, E, F, succes- 

 sive stages of transverse fission. 



stein and swims freely for a short time, soon passing, however, into 

 the ' still ' condition. The surface of the body then exudes a gela- 

 tinous excretion that hardens around it so as to form a complete 

 coffin-like case, within which little of the original structure of the 

 animal can be distinguished. Even after the completion of the cyst, 

 however, the contained 

 animalcule may often 

 be observed to move 

 freely within it, and 

 may sometimes be c 

 caused to come forth 

 from its prison by the 

 mere application of 

 warmth and moisture. 

 In the simplest form of 

 the 'encysting process,' 

 indeed, the animalcule 

 seems to remain alto- 

 gether quiescent through 

 the whole period of its 

 torpidity : SO that, how- FlG - 596. Encysting process in Vorticella micro- 

 i il .-i stoma: A, full-grown individual in its encysted 



ever long may be the state . a> r ' etracte 6 d oval circlet O f cilia ; b, nucleus ; 

 duration of its imprison- c, contractile vesicle ; B, a cyst separated from its 



stalk ; C, the same more advanced, the nucleus 

 broken up into spore-like globules ; D, the same 

 more developed, the original body of the Vorticella, 

 d, having become sacculated, and containing many 

 clear spaces ; at E, one of the sacculations having 

 burst through the enveloping cyst, a gelatinous 

 mass, e, containing the gemmules is discharged. 



mentj it emerges with- 

 out any essential change 

 in its form or condition. 

 But in other cases this 

 process seems to be sub- 



servient either to multi- 

 plication or to metamorphosis. For in Vorticella the substance 

 of the encysted body (B) appears to break up (C, D) into eight 

 or nine segments, which, when set free by the bursting of the 

 cyst, come forth as spontaneously moving spherules. Each of these 

 soon increases in size, develops a ciliary wreath within which a mouth 



