Mr. H. J. Carter on Ploesconia and Kerona. 255 



dually. Cilia now presented themselves ; the rotatory motion 

 was accelerated ; and with it the distension of the contracting 

 vesicle became greater and greater at each time, until at last it 

 thus burst the capsule, and a portion of the cilia of the Plces- 

 conia was at the same time protruded. A few minutes of rest 

 now succeeded ; and the cilia having been withdrawn, the rotatory 

 motion was again resumed, while the distension of the contract- 

 ing vesicle, also going on, at last became so great as now to 

 force a portion of the body of the Ploesconia through the rent, 

 when this vesicle again contracted, and an interval of rest fol- 

 lowed as before ; the portion of the body was then withdrawn, 

 and the same process repeated several times, until at length the 

 Ploesconia thus obtained its exit. It was now almost spherical 

 (fig. 18), from the enormous distension of the contracting vesi- 

 cle, behind which appeared the hepatic globules (b), and at the 

 circumference the legs and cilia. In this state it continued 

 stationary for some minutes, until the distensions of the con- 

 tracting vesicle, evidently increased for the bursting of the cap- 

 sule, were gradually reduced to the natural size, when the dif- 

 ferent parts of the Ploesconia regained their respective positions, 

 and the animalcule, having undergone several twitches in dif- 

 ferent directions, at last assumed its original form and bounded 

 off in quest of food. 



The capsule. — On turning to the capsule (fig. 19), this was 

 found to present an ovate elongation superiorly, upon which 

 were five lines of puucta, converging towards the small end, and 

 evidently corresponding to the ridges on the back of the Ploes- 

 conia, which I thus learnt to be granulated in the manner de- 

 scribed by Ehrenberg. In some instances, however, there was no 

 elongation ; for I had watched the evolution of P. Charon from 

 its cyst, unaccompanied by Kerona pustulata, before this, and 

 have done so since, when the five punctated lines were bent 

 meridionally over the empty cyst. 



Observations. — Thus has been described the encapsulation of 

 Kerona pustulata, followed, under the circumstances mentioned, 

 by the appearance and encapsulation of Ploesconia Charon, which 

 sequence at the time appeared to me confirmatory of M. J. 

 Haime^s conclusions respecting the metamorphosis of " Oxy- 

 tricha " into Trichoda Lynceus, especially as the remaining Ke- 

 rona-cysts were divided into three portions, and treated sepa- 

 rately in the way above-mentioned, with precisely the same 

 results. 



However, since then it has occurred to me that the absence 

 of Kerona pustulata and the sudden appearance of Ploesconia 

 Charon might have arisen from the Kerona perishing at its 

 exit, on the one hand, and from an elimination of the Ploesconia 



