the Distinctive Characters in Amoeba. 141 



now and then distinctly seen the tubular isthmus which con- 

 nects the supplementary with the primary cavity contract, be- 

 come by degrees attenuated to a mere filament, and finally part 

 in the middle, its conical- shaped ends gradually melting into 

 the boundary-wall of the primary contractile vesicle on the one 

 hand, and the supplementary vesicle on the other. 



Both seem now to be wholly independent of each other*. 

 The primary vesicle may either go on performing its diastole and 

 systole without moving from the villous margin, or may take 

 part in the pseudocyclosis. The supplementary one, again, 

 may move away to the opposite or anterior extremity of the 

 Amoeba, changing its relative position to the villous organ and 

 the primary contractile vesicle in every possible manner, and 

 apparently for an indefinite period, and may ultimately return 

 to discharge its contents independently at some portion of the 

 villous region distinct from that occupied by the primary vesicle, 

 or may actually find its way to the parent from which it sprang, 

 and coalesce with it, reappearing, or otherwise, on the next dia- 

 stole of the primary organ, as the case may be. These supple- 

 mentary contractile vesicles rarely present papillse on their sur- 

 faces ; when they do so, these are very few in number ; so that 

 it is almost impossible to determine whether the object we are 

 looking at be an ordinary empty vacuole or a contractile vesicle, 

 unless we continue our observations over a period sufficiently 

 protracted to embrace the next systolic action. 



Lastly, it is deserving of special notice, that whenever the 

 identification of one or more supplementary contractile vesicles 



** digestive spaces " at the inner extremity of the " buccal tube " of Para' 

 mecium, &c. (Annals, 2nd ser. vol. xvii. p. 357). 



* In Dr. Carpenter's ' Introduction to the Study of the Foraminifera,' 

 it is stated, on the authority of MM. Claparede and Lachmann, that in a 

 species of Amceba allied to A. princeps, after the contraction of the con- 

 tractile vesicle, from four to eight vacuoles were seen to spring up at dif- 

 ferent parts of the body, often at a considerable distance from the con- 

 tractile vesicle, and that these seemed to move towards the latter when 

 they had attained a certain size, and discharge their contents into it. In a 

 note. Dr. Carpenter states his belief that distensible vacuoles have been 

 mistaken, by some observers, for multiple contractile vesicles, but that 

 they have not the well-defined boundary of that organ, and they do not 

 present the rhythmical contractions. 



According to my experience, no vesicle, unless it be a true contractile 

 vesicle, under any circumstances bursts into the primary one. 



According to my experience, contractile vesicles or supplementary con- 

 tractile vesicles, when detached, may burst into each other, but never into 

 vacuoles, or vice versa ; I cannot help thinking, therefore, that the "va- 

 cuoles " which are here spoken of as seeming to burst into the contractile 

 vesicle must have been supplementary vesicles, not evolved spontaneously 

 in the substance of the endosarc, but disengaged and moved to a distance 

 from the primary one before the observation commenced. 



