M. J. D'Udekem on the Metamorphoses of the Vorticellse. 3 



opinions on the development of the Vorticellina^ and denies the 

 metamorphosis of the latter into Acinetce ; he thinks that these 

 two families should remain separate, and that no bond of rela- 

 tionship exists between them. 



He attacks M. Stein's opinion by well-grounded and serious 

 objections, and regards as inexact and inconclusive the observa- 

 tion by which M. Stein thought to demonstrate the metamor- 

 phosis of Vaginicola crystallina into Acineta mystacina. 



With regard to the arguments used by M. Stein, derived from 

 the simultaneous appearance of the Vorticellcs and the Acineta, 

 and the alternation of the appearance of these two Infusoria in 

 one and the same infusion, M. Lachmann objects to them as 

 proving nothing. 



In the course of the present paper I shall have occasion to 

 recur to these different objections ; for the moment, I shall con- 

 fine myself to mentioning them. 



M. Lachmann finally overturns completely the^hypothesis put 

 forward by M. Stein upon the transformation of the ciliated 

 embryos of the Acinetce into Vorticella ; he shows, by numerous 

 examples, that these embryos become transformed into Aci- 

 netce ; and he attributes the first discovery of this important fact 

 to J. Miiller. 



The essay of M. Lachmann had not yet reached Belgium, 

 last year, at the time when I presented to the Royal Academy 

 of Sciences the results of my researches upon Epistylis plicatilis. 

 The following is the resume of my observations which I gave in 

 that memoir : — 



^^ Epistylis plicatilis, before or after it has acquired its full 

 growth, becomes enveloped in a cyst, either remaining attached 

 to its style, or abandoning it, or re-uniting in one and the same 

 cyst. 



'^ Entirely enclosed in the cyst, the animal undergoes a total 

 transformation. Its mouth, peristome, and integuments dis- 

 appear by dissolving into a sarcodic liquid, in which are sus- 

 pended globules of different sizes ; the nucleus of the Epistylis 

 alone appears able to resist this solution. Upon the surface of 

 the sarcodic liquid a new resisting contractile integument makes 

 its appearance, covered with vibratile cilia, and closed at all 

 points. 



" The Epistylis is then metamorphosed into a new Infusorium 

 having much analogy to the Opalines which are met with in 

 Frogs. 



" The Opalina (we will provisionally apply this name to the 

 new Infusorium originating by the metamorphosis of the Epi- 

 stylis) revolves, and acquires such dimensions that the cyst, not 

 being elastic, bursts, and gives passage to the animal which it 



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