102 Mr. W. Addison on the Sacculi of the Polygastnca, 



I speak of the vesicles or cells being discharged " in the same 

 way/^ it is evident that I refer to the bursting, and not to imbi- 

 bition. 



Now with regard to 'imbibition/ no physical reasoning about the 

 density of fluids can have any weight in determining what living 

 structures can or cannot do ; or if it had, it would be, I presume, 

 equally cogent as regards the colourless blood-corpuscles, or the 

 pollen grain, both of which swell and burst when submitted to 

 the action of liquor potassa. If the Paramcecium aurelia be sub- 

 jected to the action of a dilute solution of the alkali, in the pro- 

 portion of half a drachm (Brandishes alkali) to an ounce and a half 



Fig. 1. 



Fig. 2. 



or two ounces of water, it immediately 

 commences a laboured, rotatory, wrig- 

 gling motion through the liquid, and 

 in many of the individuals two remark- 

 able vesicles will be seen tensely dis- 

 tended in the interior of the animalcule, 

 very frequently accompanied with three, 

 four or five perfectly transparent large 

 circular globules, projecting from the 

 body of the creature (Fig. 1.). After a 

 short period the contents of the body 

 may be seen discharging themselves into 

 one or more of these transparent projec- 

 tions, while the body itself, or rather the 

 integument of the body, may be seen to 

 shrivel up, the motionless cilia fringing 

 its circumference remaining very visible 

 (Fig. 2.)- 



Now the appearance of these transpa- 

 rent globular projections, which can be 

 formed in no other way than by the se- 

 paration and distension of the thin and 

 outermost portion of the integument (the 

 cuticle as it were), and the persistence of 



the delicate cilia when immersed in the alkaline liquid, are surely 

 quite incompatible with the idea of a solution of the integument : 

 this must be an ' inaccurate interpretation ^ of the appearances, 

 the whole of which are indeed well worthy the observation of 

 those who attend to the animalcules. 



1 remain. Gentlemen, your obedient servant, 



William Addison. 



Great Malvern, July 16tli, 1843. 



