8 M. J. D'Udekem on the Metamorphoses of the Vorticellae. 



attenuated, and seems to fold upon itself; the sarcodic sub- 

 stance traverses its integuments in all parts ; from time to 

 time it still contracts; and a complete solution soon affects the 

 whole animal, so that we find in its place merely a homogeneous 

 sarcodic liquid, containing granules, together with the nucleus, 

 which resists the general destruction. In the sarcode there 

 takes place a process which may be in some measure compared 

 with what occurs in the vitellus after the fecundation of an 

 ovum. The granules, becoming united together, form groups 

 which soon divide and subdivide ; at the same time an integu- 

 ment is formed upon the surface, in the same manner as the 

 blastoderm appears in the eggs of the inferior animals. This 

 integument is contractile, covered with vibratile cilia, and closed 

 at all points. 



The transformation is then complete ; the cyst contains a new 

 Infusorium, which may be compared to the Opalina or Bursarice, 

 which are met with in the intestines of the Batrachians. 



This description of Epistylis plicatilis may be applied in all it* 

 details to the Vorticellina in which I have observed the trans- 

 formation into an Infusorium ciliated over the whole surface. 

 It will be useless to revert to it. I shall simply indicate the 

 species in which I have observed it. This metamorphosis may 

 be found almost at will in Epistylis plicatilis ; but it is not so 

 with other species of the same genus. I have sought for it in 

 vain in Epistylis grandis and E . flavicans ; and I have only met 

 with it in the Epistylis of Tubifex, the new species of which I 

 have already spoken. 



In the genus Vorticella, I have observed this metamorphosis 

 in Vorticella microstoma, microstyla, Convallaria, and in the Vor- 

 ticella with a fringed peristome described above. 



Carchesium polypinum and arbuscula likewise undergo similar 

 metamorphoses in the interior of the cysts. 



3. Transformation of the Infusorium ciliated all over (Opalina or 

 Bursaria) into an Acineta. 



I have said, in the historical part of my essay, that M. Stein 

 was the first who sought to demonstrate the metamorphosis of 

 the Vorticelliuae into Acineta ; from what I have just said, in the 

 preceding paragraph, it may be seen that my opinion differs 

 entirely from his upon the point — that I do not suppose, with 

 him, the immediate transformation of the Vorticellina into Aci- 

 neta, but that an intermediate metamorphosis exists. 



Hence none of the arguments produced by M. Lachmann 

 against M. Stein's opinion can touch mine; I shall, however, 

 endeavour to reply to some of them, because they tend to deny 



