OF THE PROTOZOA. ACTINOPHHYINA. ' 251 



■phrys Sol, Ehr., is siuTounded by a perii^heral layer of vesicles " (he is speaking 

 of contractile vesicles), " which, when fully dilated, appear to be all of the 

 same size, to have the power of communicating with each other, and each, 

 individually, to contract and discharge its contents externally, as occasion may 

 require, though generally only one appears, and disappears, in the same 

 place." Stein describes and figures a row of vesicles immediately beneath 

 the surface of a new species he calls Actinojphrys oculata (XXIII. 24, 25), 

 but does not, hke Carter, treat them as so many contractile sacs, an interpre- 

 tation which cannot be received without much more extended inquiiy and 

 confii-mation. Notwithstanding this assertion, Mr. Carter, in his outline of 

 facts relevant to contractile vesicles in general, has the following clause, ap- 

 plying specially to the animalcules under consideration, and giving a most 

 apt illustration of the phenomena witnessed : — " In Actinophrys Sol, and 

 other Amcehce, diuing the act of dilatation, the vesicula projects far above the 

 level of the pellicula, even so much so as occasionally to form an elongated, 

 transparent, mammilliform eminence, which, at the moment of contraction, 

 subsides precisely like a blister of some soft tenacious substance that has just 

 been pricked with a pin." At another part, this same author says, generally 

 (op. cit. p. 128), and in some measure contradictoiily to the first statement 

 quoted from him, that "in Amceha and Actinoplirys the vesicula is generally 

 single ; sometimes there are two, and not unfrequently in larger Amoebcea a 

 greater number." It should be mentioned that Stein found in the animal- 

 cule, which he took to be Act. Eiclioy^nii, a superficial group of vacuola, ren- 

 dering the outline irregiilar, — a phenomenon no doubt the same as that 

 intended by Carter. Stein, moreover, described in the same animalcule two 

 contractile spaces, one at each pole, immediately beneath the surface, but 

 capable of alternately elevating themselves above, and depressing themselves 

 within it, and of thereby aiding to introduce food. 



Podophi^ya has, according to Stein and Cienkowsky (XXIII. 34, 35, 36, 

 37), a single circular contractile vesicle. Stein, indeed, figures two in one 

 specimen. So far as appears, the vesicle is not placed so close to the surface 

 as in Actinophrys. Among other structui'es mentioned by Ehrenberg, was a 

 contractile proboscis, by means of which the animalcule was supposed to re- 

 ceive food ; but other observ^ers have looked in vain for any process to which 

 such an appellation could with justice be apphed. The structure intended 

 by Ehi'enberg is, in Claparede's opinion, no other than the contractile vesicle, 

 — an opinion in which Mr. Weston seems to agree (see below), although he 

 attributes to it a structure and action without parallel in other Infusoria. A 

 glance at the quotation above made from Mr. Carter's paper will show also 

 that the contractile sac was intended. The following are the observations of 

 Claparede, referring to the matter in question: — *Trom time to time a globular 

 prominence rises slowly and gradually from a particular point on the surface 

 of the animal ; this increases more or less in difi'erent cases, sometimes, espe- 

 cially in small individuals, attaining nearly a thii^l of the size of the entire 

 body, but generally reaching only -i-th or ^ij-th of that size. The margin of 

 this projection is always well defined, much more so than the other parts of 

 the body, especially when it has attained its greatest evolution. At this 

 moment it contracts suddenly and disappears entirely, so that a flattening of 

 the outline is often to be observed at the point previously occupied by this 

 remarkable elevation : the margin soon becomes rounded again ; the globular 

 projection gradually rises, attains its previous highest development, and then 

 suddenly disappears again." The following paragraph from Mr. Weston's 

 paper {J, M. S. 1856, p. 116) refers, doubtless, to the selfsame expanding and 

 contracting process distinguished by Claparede : but the fimction of respiration 



