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



I shall not enter into any detail relative to the description of 

 the Vorticellina and the Acinetce, as this would lead too far away 

 from my subject : I refer my readers to the great work of Ehren- 

 berg, and to other general treatises on the Infusoria : I shall 

 deal with the history only from the point where the question of 

 the metamorphoses arose. 



Dr. Pineau, in an essay published in the ' Annales des Sc. 

 Naturelles^ (3 ser, iii. p. 182, and iv. p. 103), made known that 

 he had observed the Infusoria described by Ehrenberg under the 

 name of AdnetcEy become transformed into Vorticellce, No deep 

 acquaintance with microscopic studies is requisite to convince 

 any one that the observations of Dr. Pineau are deficient in that 

 exactitude which must be demanded of every conscientious natu- 

 ralist ; so that I should not attach any importance to the results 

 he supposed himself to have obtained, had he not been the first 

 who sought to establish a relationship between the Acinetce and 

 the Vorticellina. 



A few years later M. Stein published, in Wiegmann's 'Archiv' 

 (1849), his researches upon the developments of Vorticella micro- 

 stoma, Vaginicola crystallinaj and Epistylis nutans. He sought 

 to prove, by these three examples, that Infusoria belonging to 

 the family of the Vorticellina became transformed into Acineta. 

 This opinion was adopted pretty generally among the German 

 naturalists, in spite of the important adversaries it met ; in the 

 front rank of the latter must be named the celebrated Ehrenberg. 



In 1854, M. Stein published a new and very extensive work 

 upon the development of the Infusoria, and he enlarged parti- 

 cularly upon the metamorphoses of the Vorticellinse. 



He endeavoured to show that each species of the family of 

 Vorticellina has a species of Acineta corresponding to it ; that 

 ciliated embryos originate in the interior of the Acinetce ; and 

 that these ciliated embryos, when set free, become transformed 

 into Vorticellina. 



M. Stein gives this last part of his opinion only as an hypo- 

 thesis, which he considers very probable, but which he has not 

 succeeded in proving, having never been able to trace the ulte- 

 rior development of the ciliated embryo. 



This author believed that he proved the transformation of the 

 Vorticellina into Acineta, first by a direct observation upon 

 Vaginicola crystallina, then by the simultaneous presence in the 

 same infusions of numerous species of Vorticellina and corre- 

 sponding species of Acinetce, and finally by the alternate appear- 

 ance of Vorticellina and Acinetce in the same infusion. 



Last year appeared a very remarkable essay on the Infusoria, 

 by M. Lachmann*, in which he strongly attacks M. Stein's 

 * Annals of Natural History, ser. 2. xix. pp. 113, 215. 



