CHAPTER XVIII 



MASTIGOPHORA AND PROTOMON ADINA 



Mastigophora — Eufiagellata^ — Protomonadina- — Monozoa — Oicomonadidae 

 — Bodonidse — Cercomonadidae — Tetramitidae— References. 



MASTIGOPHORA Diesing, 1866. 



Definition.-7-Plasmodromata with one or more permanent flagella 

 which serve as organs of locomotion, and at times for the capture 

 of food. 



Morphology. — ^The Mastigophora are usually microscopical in size, 

 but have a tendency to colony formation. 



The ectoplasm is present in the form of a sheath called the peri- 

 plast, a term which is really botanical in its meaning. The peri- 

 plast contains contractile elements called myonemes. The fiagellum 

 may be situate anteriorly (tractellum) or posteriorly (pulsellum); 

 there may be but one (monomastigote), two, or four of equal length 

 (isomastigote), one long and one short (paramastigote) ; one anterior 

 and one posterior (heteromastigote); several flagella placed together 

 (polymastigote), or numerous flagella scattered over the body 

 (holomastigote). 



The typical flagellum consists of an elastic axial core more or less 

 enclosed in a contractile sheath from which the ' end-piece ' projects. 

 It takes its origin fr6m a granule situated in the cytoplasm, and 

 apparently forming only a swelling at its base. The swelling is, 

 however, a centrosome, to which various names have been applied, 

 such as basal granule or blepharoplast. Sometimes this centro- 

 some is contained in a special nucleus which is called a kineto- 

 nucleus. The centrosome-blepharoplast may be single, when there 

 is only one flagellum; or multiple, when there are many flagella. 

 The flagellum may, however, penetrate deeper into the cytoplasm, 

 until it reaches the nucleus. This prolongation is called the rhizo- 

 plast, which may represent the central spindle (centrodesmose) of 

 the achromatic elements of the dividing nucleus, and which connects 

 the divided portions of the original centrosome; or it may have 

 arisen simply as an outgrowth from the blepharoplast. Thus, the 

 various parts of the flagellum may be rhizoplast, blepharoplast, 

 sheath or envelope, and end-piece. 



If the centrosome is single, it may be intra- or extra-nuclear, 

 and ill either case is a centrosome-blepharoplast; if multiple, the 

 portion connected with the nucleus is the centrosome, and that 

 connected with the flagellum is the blepharoplast. 



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