PROTOPLASMIC MOVEMENT. 389 



was then removed from the warm chamber and cooled gradu- 

 ally to the temperature of the room, 12° C. At o changes of 

 shape commenced again, and at p were already quite active. 



When the temperature exceeds the maximum the proto- 

 plasm dies at a certain degree, which may be called the ultra- 

 maximum, and exhibits suddenly a shrinking and loss of 

 clearness, on account of the coagulation of the albumens, and, 

 as a rule, the vacuoles are extruded. This heat-death or last- 

 ing heat-rigor may also come about even at a lower tempera- 

 ture when the warming has been very long continued. Sub- 

 sequent cooling then naturally produces no further change. 



Freshwater AmcEbse which, after warming for one minute at 

 35°, showed only passing rigor, Kiihne found would, after 

 fifteen minutes' warming at the same temperature, become 

 completely globular and lose all power of movement. After 

 shorter warming of Amoebse at 40° they appeared like ''glo- 

 bular, sharp, and doubly-contoured vesicles, which contained 

 a brownish-looking and, by transmitted light, very opaque 

 lump, which was generally attached firmly to one side of the 

 periphery, and filled up some three parts of the spherical space. 

 The remaining space was filled with a transparent clear fluid, 

 in which small granules in active molecular movement swarmed 

 about." Kiihne subsequently treated such individuals with 

 water at 45° ; the molecular movement in the previously clear 

 portion of the vesicle stopped, and formed here also a firm 

 coagulum.^ 



When the protoplasm enters suddenly into heat-rigor it has 

 no time to change its form. Max Schultze^ saw, for instance, 

 the protoplasmic threads of Miliola, when warmed quickly, at 

 any rate up to 45°, enter at once into rigor : similarly with 

 Tradescantia. 



Concerning the value of the maximum and ultramaximum 

 for difi'erent species of contractile protoplasm, the following 

 table gives some idea : 



1 W. Kiihne, ' Untersuchungeu iiber das Protoplasma,' pp. 43 — 45. 

 ^ M. Schultze, ' Das Protoplasma, &c.,' p. 22, 



