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



union of the posterior two-fifths of the body. Abdominal 

 cavity containing sarcode charged with molecules, refractive 

 globules as in Ploesconia, dark angular grains, and, when 

 present, digestive spaces more or less filled with fragments 

 of food, but no hepatic cells like those of Nassula, &c. Con- 

 tracting vesicle on the left side, marginal, posterior, and op- 

 posite to the termination of the gill. Nucleus long, cylin- 

 drical, occupying the greater part of the left side, sometimes 

 divided into two portions, and even more when the Kerona is 

 about to become encapsuled. Posterior and lateral margins 

 more or less round, fringed with cilia. The anterior margin, 

 with the wreath of cilia, the gill, and the triangular or buccal 

 depression leading to the mouth, so much the same as in 

 Ploesconia that, with the illustrations of K. pustulata, they do 

 not need a separate description. Length varies; when full- 

 grown, about 1 -200th of an inch. 

 Hab. Salt and fresh water, generally in company with Ploesconia 

 Charon, but not always ; feeding on small animalcules, Diato- 

 macese and Algae. 

 Loc. Island of Bombay and Europe. 



Obs. This animalcule dificrs very much in size, appearance, 

 and development, according to its age and the amount of 

 nourishment where it may be living. When young, the anterior 

 legs are by no means evident ; and this makes it look very much 

 like an Oocytricha, for which it appears to me to have been taken 

 in the instances to which I shall presently allude. The legs, how- 

 ever, become plainly visible when it is a little older and larger, 

 which conditions may be brought about by adding a little glue 

 to the water, as this offers a palatable nourishment, which not 

 only keeps the animalcule alive, but leads to its full development, 

 especially if it be in salt water. The salt, too, somewhat delays 

 the diffluence after death ; and if a little of the water be dropped 

 upon a glass slide, so as to assume a globular form as much 

 as possible, and then left to evaporate until it is nearly flat, 

 these animalcules will have congregated together in the centre, 

 and under a light piece of thin glass will be sufficiently con- 

 trolled in their movements and remain sufficiently long without 

 diffluence to be observed most satisfactorily. 



The nucleus, although represented as consisting of a single 

 cylindrical organ in the illustrations, is often seen to be divided 

 into two portions, and even into four just previous to encapsu- 

 lation, when it disappears altogether, apparently by dissolution*. 

 Thus, with the nucleus divided into two portions, and the con- 

 tracting vesicle on the left side opposite the termination of the 



* This division of the nucleus into two portions has also been noticed 

 by M. Balbiani (Comptes Rendus, and Annals, vol. ii. p. 443, 1858). 



