Protomyxa. 59 



At one period of its existence Protomyxa exists as a 

 minute Protamceba-Xfot creature (fig. 8*) possessing the gene- 

 ral characters already described as possessed by that form. 

 Numbers of these Protafnaba-\&. bodies unite to form a large 

 aggregation of protoplasm, to which the name of plasmo- 

 dium is given (fig. 8/). The plasmodium behaves exactly 

 like a large Prdiam&ba, throwing out and retracting pseudo- 

 podia, engulfing food particles, &c. The individuals going 

 to form a plasmodium cannot, however, be distinguished 

 in its mass as individuals ; their identity becomes lost. 

 After a time, however, the plasmodium comes to rest and 

 the pseudopodia are withdrawn. The mass collects into a 

 round ball which soon becomes covered by a capsular invest- 

 ment or cyst ; hence this stage is spoken of as the encysted 

 stage (fig. 8#). Subsequently the protoplasm within the 

 cyst becomes segmented or divided into distinct masses 

 forming a mulberry-like bunch within the cyst (fig. 8/). 

 Under certain conditions the cyst bursts and the separate 

 protoplasmic masses escape (fig. 8<r). Each unit is an 

 actively moving pear-shaped mass of protoplasm, possessed 

 of a. fine flagellum or whip at the pointed end by the con- 

 stant motion of which the little organism is propelled 

 through the fluid medium. This motion is, however, transi- 

 tory, for the flagellate mass speedily becomes more and 

 more sluggish in its movements, and ultimately comes to 

 rest, drawing in its flagellum and developing pseudopodia 

 like those of the form we started with. Such are the stages 

 in the life-history of this important type, and they are of 

 sufficient interest to warrant more detailed treatment before 

 we proceed to the considerati6n of higher forms. 



In the first or amoeboid stage we have to note especially 

 the apparently exceeding simplicity of structure accompanied 

 by complexity of function. In other words, we have in this 

 stage complete physiological differentiation without corre- 

 sponding morphological differentiation. 



Passing to the second or plasmodial stage, we have 



