APPENDIX D. xcv 



Ciliated Infusoria. Stein declares 1 that within the body 

 of Actinophrys sol, and also within that of Podophrya fixa, a 

 ciliated germ is often produced, which subsequently develops 

 into a Vorticella. Cienkowski believes that the Actinophryna 

 of Stein were really Acinetina, though he also declares he 

 has seen the development of ciliated embryos within the 

 latter, which however give rise, not to VorticellcE, but to 

 organisms similar to those from which they have arisen. 

 Stein would make Acinetina a mere developmental phase in 

 the life-history of Vorticellma, whilst the observations of Cien- 

 kowski would tend to establish them as a distinct and 

 separate family. Mr. Carter's 2 observations, again, are partly 

 in accord with those of Stein, since he says he has frequently 

 seen the passage of Vorticella into Acineta; though they are 

 otherwise in agreement with those of Cienkowski, since he 

 says he has never seen the young of Acineta assume any 

 other form than that of Acineta. 



Stein believes that encysted VorticellcB, after undergoing 

 certain metamorphoses within their cyst-wall, may be con- 

 verted, according to the influence of external conditions, 

 either into an Actinophrys or into a Podophrya. The creatures 

 so produced are then thought to give birth to a ciliated 

 embryo, which is at first lodged within a definite cavity in 

 the substance of their body. The embryo is pear-shaped, 

 with a central constriction, and it is provided with one or 



the liberated segments. . . . Cilia could riot be perceived over the 

 whole surface. . . . After waiting patiently for twenty minutes, I saw 

 the motion cease; and, at the same time, short tentacles made their 

 appearance, which were protruded more and more ; and in a few 

 minutes afterwards the segment regained the spherical form : thus, 

 after moving about freely for a time, it was again transformed into 

 a Podophrya.' This was witnessed, Cienkowski tells us, by other 

 observers as well as himself, and the phenomena are in some respects 

 comparable with what takes place in the formation of the ciliated spore 

 of Vaucheria. (See vol. i. p. 175.) 



1 ' Die Infusionsthiere auf ihre Entwickelungsgeschichte,' Leipzig, 1854- 



2 ' Ann. of Nat. Hist.,' 1857, vol. xix. p. 260. 



