24 



GENERAL HISTORY OF 



soria can accommodate themselves to different fluids, provided that 

 the transition be not too sudden. Thns, similar species may be 

 found in rivers, at their soiu'ce, where the water is perfectly fresh, 

 and at theii* very mouths, or junction with the salt water of the 

 ocean. Hydatinea have been fed upon powdered rhubarb without 

 being sensibly affected by it ; nor does calomel or corrosive sublimate 

 kill them ; at least they live some time after these have been mixed 

 with the water. Strychnia causes instant death. 



Mr. Addison states that liquor potassse, produces on the smaller 

 forms of the Polygastric animals, "the same effect as it does on the 

 colourless blood and pus-corpuscles of mammalia ; it peneti'ates the 

 transparent integument of the animalcule by imbibition, and causes 

 it to burst open and discharge its contents, which have the same 

 appearance as the molecules and granides, from the colourless blood 

 and pus-corpuscles. 



In the larger forms of the polygastric animalcules, the large 

 vesicles or cells (called stomachs) veiy visible in their interior, are 

 all discharged fr'om the bodies of the creatiu'es in the same way, 

 when submitted to the action of liquor potassae. Thepc so-called 

 stomachs may be seen enlarging in the interior of the animalcule, 

 prior to the rupture of the external integument ; and when they are 

 discharged from the body of the animalcule, numerous minute mole- 

 cules may be noticed within them. 



If the Paramecium aurelia be subjected to the action of a dilute 

 solution of the alkali, in the proportion of half a drachm (Brandish's 

 solution) to an ounce and a half or two oimces of water, it imme- 

 diately commences a labom-ed rotatory wriggling motion thi'ough the 

 liquid, and in many of the individuals, two remai'kablc vesicles will 

 be seen tensely distended in the interior of the animalcule, very 

 frequently accompanied with three, four, or five, perfectly ti'anspa- 

 rent large cii-cular globules, projecting from the body of the creature. 

 After a short period the contents of the body may ])e seen dischai'ging 

 themselves into one or more of these transparent projections, while 

 the body itself, or rather the integument of the body, may be seen 

 to sluivel up, the motionless cilia fi-inging its circumference remain- 

 ing very visible." (On the sacculi of the Polygastrica, Annals of 

 Natural Histoiy, vol. 12, 1843, p. 101.) . 



