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



Having early become sensible of this, I have, during my micro- 

 scopic investigations, taken advantage of the opportunities that 

 have come before me of sketching and describing these animal- 

 cules when they have appeared under favourable circumstances ; 

 and although these have only happened now and then, yet, in 

 the absence of a special report upon the subject, it is hoped that 

 they may prove acceptable. 



In reviewing them for publication, I find, however, that they 

 will not admit of my describing with certainty more than two 

 species of Plcesconia and one of Kerona, which are not only the 

 most common in the salt and fresh water of the marshes in the 

 island of Bombay, but, according to Dujardin's accounts, equally 

 common in Europe, and, being respectively perhaps the best of 

 their types, will do as well there as here for conveying the best 

 idea of the structure and organization of the whole. In com- 

 piling the illustrations, too, I have endeavoured to facilitate the 

 reader's acquaintance with these animalcules by shading them 

 as opake or semi-opake objects, and not transparent, as they 

 really are in nature, since it is impossible to give a clear idea of 

 their forms unassisted by actual observation, if both the upper 

 and lower surfaces are represented in the same figure; the 

 appendages, too, have severally been slightly exaggerated and 

 artificially placed, in order that they may be better seen ; but, 

 although these liberties have been taken, the deviation from 

 nature is so trifling, that, for the object for which they are in- 

 tended, they may be considered almost correct. To view them 

 as perfectly accurate is not my wish, since there may be a leg 

 too little or too many ; but I can vouch for their being better 

 in this respect than those of Ehrenberg and Dujardin, whose 

 deficiencies, rendered more confusing by their having repre- 

 sented these animalcules with their natural transparency, in 

 which all their parts are seen at once, chiefly induced me to 

 adopt the opake shading above mentioned. 



Among other observations, I have had the opportunity of 

 witnessing the encapsulation of one of the Plcesconia and the 

 Kerona, together with their subsequent changes and the elimi- 

 nation of the former, all of which, bearing strongly on the meta- 

 morphosis of the " Oxytricha " into Trichoda Lynceus, described 

 by the late M. J. Haime*, to which I have above alluded, will also 

 be detailed and illustrated. 



In my descriptions, I would also have it remembered that 

 everything therein mentioned has been seen by myself, unless 

 otherwise stated, in order that it may not be supposed that I am 

 merely repeating the observations of those who have gone before 



* Ann. des Sc. Nat. .3 ser. t. xix. p. 109, Zool. 1853. 



