Dr. C. F. J. Lachmann on the Organization of Infusoria. 235 



that it seems to have led him to the incorrect assertion*, that 

 he had " by direct observation " seen Vaginicola crystallina be- 

 come converted into Acineta mystacina. But even this observa- 

 tion was not exact. On a number of filaments of Confervse 

 which he had thrown into a glass filled with clear spring- water, 

 because they were particularly rich in VaginicolcE, Stein found, 

 after the lapse of several days, " instead of the VaginicolcB scarcely 

 anything but Acinetce/' Stein does not say that he convinced 

 himself that at the commencement there were no Acineta at all 

 adhering to the Confervse, or that he obtained any certainty as 

 to the identity of the individuals by the identity of the spot on 

 which an Acineta sat with that to which a Vaginicola was pre- 

 viously attached, — two things which certainly ought to have 

 been done in order to prove a direct observation of the transi- 

 tion of one form into the other ; and yet, as he could not find 

 the sheaths of the Vaginicolce, which had probably fallen down, 

 he allows himself to be led away into a bold hypothesis, which 

 is to solve the difficult problem of the conversion of the hard 

 sheath of the Vaginicola, which is widest at the bottom, into an 

 ^cmete-sheath, which is narrow at the base. 



I now endeavoured to settle the existing doubts by strict iso- 

 lation. For three years I have efiected this, at different times, 

 with different Vorticellina, namely with Vorticella microstoma, 

 campanula, and nebulifera; Carchesium polgpinum; Epistylis 

 plicatilis, and Opercularia nutans : on each occasion I preserved 

 about twenty or thirty individuals of one of the above-mentioned 

 species, sometimes in a small glass tube, sometimes on an ob- 

 ject-glass, keeping them moist, and preventing desiccation by 

 the occasional addition of distilled water. In this way I ob- 

 tained cysts of Vorticella microstoma often enough, but no Act- 

 netince were ever developed either from this or from the other 

 Vorticellince. From the cysts of Vorticella microstoma unaltered 

 Vorticella escaped, sometimes at the end of three or even four 

 weeks. 



After I had convinced myself that the conversion of Vorticella 

 into Acineta was not to be proved in this way, but was rather 

 rendered more improbable by the experiments instituted, I 

 attempted to test the other part of Stein^s hypothesis, — to 

 ascertain the fate of the embryo of Acineta. An observation of 

 Professor J. Miiller, which renders probable the conversion of 

 such young animals into an Acineta resembling the parent, has 

 already been adduced. Subsequently I succeeded several times 

 in obtaining a certain result. In order to facilitate observation 

 and avoid confounding the roving embryos with similar animals, 

 I generally isolated each Acineta, containing one or two em- 

 * L. c. supra, p. 36. 



