Mr. H. J. Carter on the Organization of Infusoria. 127 



and the buccal cavity of encysted Vorticella becoming filled with 

 fluid the moment it disappears (where we know it to be attached 

 to the buccal cavity, and not to the pellicula), are almost conclu- 

 sive of its excretory office. We have now to find out how this 

 fluid is brought to the vesicula. 



It will be remembered that there is a series of fusiform sinuses 

 which surround each of the vesiculse in Paramecium aurelia, and 

 some other animalcula of this class, on which Spallanzani made 

 the important observation, that as they become empty the vesi- 

 cula becomes filled*. This may be easily seen^ as well as that 

 they do not reappear until some time after the vesicula has con- 

 tracted. Thus we infer, that the fluid with w^hich the vesicula 

 is distended comes through the sinuses, but is not returned by 

 them to the body of the Paramecium. 



Now in some cases, faint hyaline or transparent lines may be 

 seen to extend outwards f from each of these sinuses, which lines, 

 Eckhard has stated, " traverse the body in a stellate manner." 

 Hence, when we add Eckhard's evidence (which I have been able 

 to confirm in a way that will be presently described) to the ob- 

 servation of Spallanzani, and connect this with the facts already 

 adduced in favour of the excretory office of the vesicula, it does 

 not seem unreasonable to conclude that the whole together 

 forms an excretory vascular system, in which the vesicula is ihe 

 chief receptacle and organ of expulsion. 



While watching Paramecium aurelia, I on several occasions 

 not only observed that the vesiculse were respectively surrounded 

 by from seven to twelve pyriform sinuses of different sizes, and 

 that lines extended outwards from them in the manner described 

 by Eckhard ; but I further observed that these lines were com- 

 posed of a series of pyriform or fusiform sinuses, which diminished 

 in size outwards ; and frequently I could trace as many as three 

 in succession, including the one next the vesicula (fig. 66 bb). 

 Hence I am inclined to infer, that this vascular system through- 

 out is more or less composed of chains of such sinuses, and that 

 all have more or less contractile power like that of the vesicula. 

 Just preceding death, when Paramecium aurelia is compressed, 

 and under other favourable circumstances, these sinuses run 

 into continuous hyaline lines, and may not only be seen extend- 

 ing in a radiated, vascular form across the animalcule, but even 

 branching out round the position of the vesicula, which, having 

 now become permanently contracted, has thus poured back the 

 contents which render them visible (fig. 07 b b). They enter 



* Spallanzani ap. Dujard. op. cit. p. 103; Spall. Opusc. Phys. trad. 

 Fran?, t. i. p. 248. 

 t Ann. & Mag. Nat. Hist. vol. xviii. p. 448, 1846. 



