MORPHOLOGY 49 



Locomotor organellae 



Closely associated with the body surface are the organellae of 

 locomotion: pseudopodia, flagella, and cilia. These organellae are not 

 confined to Protozoa alone and occur in various cells of Metazoa. 

 All protoplasmic masses are capable of movement which may result 

 in change of their forms. 



Pseudopodia. A pseudopodium is a temporary projection of part 

 of the cytoplasm of those protozoans which do not possess a definite 

 pellicle. Pseudopodia are therefore a characteristic organella of 

 Sarcodina, though many Mastigophora and certain Sporozoa, which 

 lack a pellicle, are also able to produce them. According to their 

 form and structure, four kinds of pseudopodia are distinguished. 



1). Lobopodium is formed by an extension of the ectoplasm, 

 accompanied by a flow of endoplasm as is commonly found in 

 Amoeba proteus (Figs. 46; 184). It is finger- or tongue-like, sometimes 

 branched, and its distal end is typically rounded. It is quickly 

 formed and equally quickly retracted. In many cases, there are 

 many pseudopodia formed from the entire body surface, in which 

 the largest one will counteract the smaller ones and the organism 

 will move in one direction; while in others, there may be a single 

 pseudopodium formed, as in Amoeba striata, A. guttula, Pelomyxa 

 carolinensis (Fig. 186, b), etc., in which case it is a broadly tongue- 

 like extension of the body in one direction and the progressive move- 

 ment of the organisms is comparatively rapid. The lobopodia may 

 occasionally be conical in general shape, as in Amoeba spumosa (Fig. 

 185, a). Although ordinarily the formation of lobopodia is by a gen- 

 eral flow of the cytoplasm, in some it is sudden and "eruptive," as in 

 Entamoeba blattae or Entamoeba histolytica in which the flow of the 

 endoplasm presses against the inner zone of the ectoplasm and the 

 accumulated pressure finally causes a break through the zone, result- 

 ing in a sudden extension of the endoplasmic flow at that point. 



2). Filopodium is a more or less filamentous projection com- 

 posed almost exclusively of the ectoplasm. It may sometimes be 

 branched, but the branches do not anastomose. Many testaceans, 

 such as Lecythium, Boderia, Plagiophrys, Pamphagus, Euglypha, 

 etc., form this type of pseudopodia. The pseudopodia of Amoeba 

 radiosa may be considered as approaching this type rather than the 

 lobopodia. 



3). Rhizopodium is also filamentous, but branching and 

 anastomosing. It is found in numerous Foraminifera, such as 

 Elphidium (Fig. 5), Peneroplis, etc., and in certain testaceans, such 



