PKOTOPLASMIC MOVEMENTS. 



75 



FIG. 35. 



one another, and thus the products of any chemical changes taking 

 place at any given part of the cell body are rapidly distributed 

 over the entire mass of the protoplasm. 



If there be no definite cell wall as in naked vegetable spores, 

 and amoeboid forms of animal life to restrict or direct the cur- 

 rent of protoplasm, it flows out in various directions in budlike 

 processes, which appear at various parts of the protoplasmic mass, 

 so as to cause a constant change in the form of the cell. These 

 outstretched processes sometimes flow together and unite com- 

 pletely, often inclosing some of the medium in which the creature 

 is suspended, or catching some foreign particle floating near them. 



The flowing out of these pseudopodia commonly takes place for 

 some little time persistently from one side of the cell ; and the 

 body of the cell, as it were, has to 

 follow the protrusion of the pro- 

 cesses in such a manner that in a 

 little time definite change in posi- 

 tion or movement in a certain di- 

 rection occurs; thus the unit of 

 protoplasm may be said to perform 

 definite progression of locomotion. 

 All these movements may be seen 

 in the white blood corpuscles of a 

 cold-blooded animal, such as afrog, 

 and still more easily in the unicel- 

 lular being known as amoeba. 



Various influences may be seen 

 to affect the rate of movements, 

 and probably influence at the same 

 time the other activities of the protoplasm. Foremost among 

 these must be named : (1.) Temperature. If a protoplasmic unit 

 which is observed to be motile be gently warmed, the movements 

 become more and more active as the temperature is raised, until 

 at a certain point, about 35-42 C., a spasm occurs, resulting in 

 the withdrawal of the pseudopodia ; soon after which the cell as- 

 sumes a spherical shape. If the heat be carefully abstracted by 

 the gentle and short application of cold, the protoplasm may be 



An amoeba figured at two dif- 

 ferent moments during movement, 

 showing a clear outer layer and a 

 more granular central portion. 

 (n) Nucleus; (i) Ingested food. 

 (Gegenbauer.; 



