THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 16. APRIL 1859. 



XXVI. — On Ploesconia and Kerona. 

 By H. J. Carter, Esq., Bombay. 



[With a Plate.] 



There are no animalcules more interesting than Ploesconia and 

 Kerona, from their being the highest of the class of Infusoria 

 in point of development, whilst there are none more difficult to 

 study, on account of their complicated structure, incessant mo- 

 tion, transparency, and rapid diffluence or change of form after 

 death ; so that, on the one hand, while they attract notice from 

 their position, they, on the other, almost elude acquaintance, 

 without the most prolonged watching under the most favourable 

 circumstances; hence, probably, the imperfect way in which 

 they have hitherto been described and delineated. 



All who have given their attention to the Infusoria generally 

 must be aware of the unsatisfactory details which we possess of 

 the PloBsconice and Keroncs, and therefore of the desirableness of 

 obtaining more precise information respecting them, that it may 

 be really known how near the highest animalcules approach 

 those forms with which we are most conversant among the In- 

 vertebrata. 



At first sight the Plcesconits have very much the appearance 

 of insects, and hence they have been called " water-spiders ;" 

 but although they outwardly resemble the Articulata, and, in- 

 deed, approach them in form, as will be presently seen, yet their 

 internal organization remains strictly Infusorial. Again, one 

 has been described as also undergoing a metamorphosis in its 

 development, something like insects, which gives the family 

 additional interest ; so that altogether there are many reasons 

 for subjecting these animalcules to further and more rigid ex- 

 amination. 



Ann. b^ Mag, N. Hist. Ser, 3. Vol.m. 16 



