Minute Anatomy of the Infusoria. 473 



there exists a second, which I surmised some years ago at first 

 sight of the Vorticella-cysts, but which I was so fortunate as to 

 discover only in the last summer holidays. An immense number 

 of my Vorticella had become encysted, and I determined to ex- 

 amine them daily so as to observe once more through all its 

 stages the metamorphosis into Acineta-forms which 1 had pre- 

 viously seen so distinctly, and then to follow the further course 

 of the offspring of these Acinetce. In order to get rid of all foreign 

 forms of Infusoria, which might possibly have produced a de- 

 ception, from my further observations, I selected, on this occa- 

 sion, the mud at the bottom of the infusion, in which innume- 

 rable Yorticella-cysts lay scattered, and poured off all the water ; 

 I then rapidly evaporated the moisture contained in this mud 

 until it was perfectly dry. The remainder just baked to its sup- 

 port, was, after the lapse of a day, scraped off, and fresh spring 

 water, in which, as is well known, Infusoria are of rare occur- 

 rence, was poured over it. On re-examining the softened mud, 

 I found my Vorticella-cysts in capital condition ; every free infu- 

 sorial organism had however disappeared, as might naturally be 

 expected. 



To my great astonishment, within twelve hours later I found 

 at the surface of the infusion a considerable number of free Vor- 

 ticell-ce, all of the normal size or considerably larger, and of these 

 a few became encysted again under my inspection. 



In the course of a clay all these free Vorticellce had disappeared 

 again, and they did not reappear subsequently. The consider- 

 able size and number of the Vorticellce, and the fact that the in- 

 fusion wa> covered, testify that these Vorticellce had not come from 

 without, during the twelve hours that had elapsed since the last 

 examination ; they must then have arisen from the cysts In- 

 voluntarily breaking out of them. Probably these were such 

 VorticelliE as would not have become encysted of themselves, but 

 were constrained to do so when the evaporation of the water 

 threatened them with death. 



In the following days the alterations in the interior of the 

 Vorticella-cysts were limited to the change of the merely sphe- 

 rically contracted Yorticella-body into a simple, closed, round 

 vesicle, in which no traces of the original organization of the 

 Vorticella were any longer to be detected. The contents of the 

 cyst were now perfectly similar to those of a simple cell with 

 sometimes coarsely granular, sometimes finely granular contents, 

 amidst which the unchanged band-like nucleus, and a clear un- 

 changeable space, lay imbedded. After about a week's watching 

 for further changes, I perceived that in many cysts the included 

 parental vesicle became sacculated-looking and uneven, and that 

 in its interior many considerable hvaline spaces arose, which 



Ann. ^ Mag. X. /fist. Ser. 2. VoLh. 31 



