78 VORTICELLSE. PART in. 



not fall off but subdivide in the same manner, it follows 

 that, by successive divisions, a whole group of these 

 beautiful animals may spring from the same stem, as 

 in fig. 107. 



The Yorticella has a most wonderful mode of repro- 

 duction common to a few other Infusoria. A gelatinous 

 substance is secreted by the bell, which hardens and 

 envelopes it in a cyst; the encysted bell then separates 

 from its stalk, and is transformed into an infusorial 

 animal called an Acineta (fig. 108), closely resembling the 

 Actinophrys sol with radiating filaments which it conti- 

 nually stretches out and draws in. A motile ciliated 

 embryo, or Vorticella bud, is then formed within the Aci- 

 neta, which, after a time, comes out at a slit in its side, 

 swims about, gets a stem, fixes to some object, and is de- 

 veloped into a Yorticella. The slit closes again, and the 

 Acineta keeps moving its filaments as usual, and another 

 motile embryo is formed within it, which is emitted by 

 a slit in the same manner, and is also developed into a 

 Vorticella. As these young Vorticellse, or bell animals, 

 may undergo the same transformations, there may be an 

 indefinite alternation of the two forms. The Vorticella- 

 bud, when it issues from the slit in the Acineta, has an 

 oval form, with a circlet of long cilia at its narrow end, 

 a mouth at the more obtuse, a nucleus, and contractile 

 vesicles, and, after swimming about till it finds a suitable 

 place, it becomes fixed by one end of its oval body, a 

 style or stem is formed, which rises rapidly, and the 

 adult shape is developed. The Acinetse are said to live 

 upon Infusoria : they apply the dilated apex of their rays 

 as sucking discs to the animal, and suck its contents 

 till it dies. The Tricoda linceus undergoes metamor- 

 phoses analogous to those of the Yorticella, but more 

 numerous and complicated. 3 



Most of the Vorticellse, and probably the majority of 



3 Described in ' The Microscope,' by Dr. Carpenter. 



