200 PROTOPLASM. 



movements exhibited by naked protoplasm, no substantial dif- 

 ference can be seen beyond that which depends upon the con- 

 finement of the mass in one case within practically rigid walls. 

 The naked protoplasm moves slowly from place to place, by 

 thrusting out an irregular projection which soon enlarges, and 

 in its turn gives out new projections, while the mass behind is 

 slowly moving up. This movement is identical with that observed 

 in the amoeba. In the substance of a mass of naked proto- 

 plasm granules can be seen to move in varying channels ; and 

 this corresponds strictly to the movement known as the circu- 

 lation. Moreover, in the naked protoplasm larger or smaller 

 vacuoles (see 120) are observed to increase and diminish in size, 

 their limiting walls answering essentially to the threads before 

 described. 



551. Rotation of protoplasm in cells. The film of protoplasm 

 in contact with the cell-wall does not generally share in the 

 movement of the softer part which it encloses, but usually re- 

 mains entirety stationary, or else very slowty shifts its posi- 

 tion on the wall. In some cases, however, the whole mass 

 of protoplasm slowly revolves on its own axis, canying with 

 it all imbedded matters. This movement should be called 

 rotation ; but the term is often employed interchangeably with 

 circulation. 



552. Rate of protoplasmic movements. In the cells of the 

 shaft of an} 7 Chara which has transparent walls for instance, 

 Nitella the rapid movement can be very clearly seen to be 

 confined to the interior of the protoplasm, the outer part in which 

 chlorophyll-granules are imbedded not moving to any great ex- 

 tent, if indeed at all. At its interior the protoplasm moves with 

 what seems under the microscope to be a very rapid rate ; it is, 

 however, absolutely very slow ; being only about one and a half 

 millimeters per minute, at a temperature of 15 C. 



553. The rate differs considerably in different plants; for 

 instance, according to several observers, the distance traversed 

 in one minute at a temperature of 15 C. is as follows : 



Name of plant. mm. Observer. 



Potamogeton crispus, leaf-cell . . . .009 . . . Hofmeister. 



Ceratophyllum demersum, -leaf-cell . .094 . . . Mohl. 

 Tradescantia Virginica, stamen-hair . .137 



Sagittaria sagitttefolia 174 ... Mohl. 



Vallisneria spiralis 225-1.086 . Mohl. 



Hydrocharis Morsus-ranae, root-hair . .543 



Nitella flexilis, cells of the shaft . .1.500-1.600 . Nageli. 



