250 Mr. H.J. Carter un Ploesconia and Keroiia. 



articulations like those of the Articulata, but so transparent that 

 they can only just be seen now and then when the light is 

 favourable ; and in the cleft terminations of the posterior ones 

 there is a resemblance to the divided termination of the leg 

 generally, but more particularly to the setiferous legs of the 

 Entomostracous Crustacea; besides, we have a gill-like appa- 

 ratus at the side, which would appear to have a different func- 

 tion (perhaps respiratory) from that of the wreath of cilia in 

 front, with which it is continuous, the office of which is distinctly 

 to bring the particles of food to the oral orifice, and which, 

 again, might be considered analogous to the palpi. But here 

 all resemblance ceases, siuce there is no defined alimentary canal 

 (although there may be a distinct alimentary cavity), and there 

 is the organ called the " gland " or " nucleus,^" which is essen- 

 tially a character of the Infusoria, and the contracting vesicle, 

 which does not, so far as my observation extends, appear in 

 any of the Entomostracous Crustacea, — that which I formerly 

 stated to be a contracting vesicle in the " Water-flea,'^ or young 

 of Cyclops, being merely contractions of the last part of the 

 alimentary canal*. 



Another remarkable difference between the Ploesconm and 

 higher Invertebrata is the phEenomenon of " diffluence,'' which 

 takes place at death, when a part or the whole of the body, 

 according to the amount devitalized, disintegrates — as a bunch 

 of iron-filings held together by magnetism falls to pieces when 

 that fluid is abstracted. 



Thus the study of the Ploesconia points out to us that a com- 

 plicated structure is not necessarily a more cohering one, none 

 the less simple because it cannot be seen, — facts which should 

 be borne in mind v/hen we would limit structure and organiza- 

 tion by the powers of the microscope, and intricacy of form by 

 want of molecular tenacity. 



Among the Ploesconia I would include all Ehrenberg's Euplota, 

 together with his Aspidisca Lynceus [Trichoda Lynceus), which 

 is very common in Bombay, and essentially of the type of Ploes- 

 conia ; but not his Diophrys, I think ; and most certainly not his 

 Loxodes, which, with Chlamidodon, is more nearly allied to Kol- 

 poda, Ehr. ; at all events, they are not Ploesconia. 



Of the Kerona 1 am not prepared to state more in this respect 

 than is mentioned in the observations after the species which I 

 have described. 



Generation. — Multiplication by longitudinal and transverse 



division in Ploesconia and Kerona has been already mentioned, 



and budding in the latter; but I have not seen budding in 



Ploesconia. Disparity in size under longitudinal division, as 



* Annals, vol. xviii. p. 129, 1866. 



