CHAPTER XII 



SYSTEMATIC REVIEW OF THE PROTOZOA : THE 



MASTIGOPHORA 



THE distinctive feature of the class Mastigophora is the possession 

 of one or more flagella as organs of locomotion and food-capture, 

 not merely during early stages of development, but in the active 

 phases of the adult organism also. In other classes, as has been 

 pointed out in a previous chapter, flagella may be present in the 

 young stages, but are absent in the adult phases. In the Masti- 

 gophora a flagellum is a permanent feature of the organization, 

 though even in this class it may be temporarily lost, either in 

 active phases, when the animal may become amoeba-like, or in 

 resting phases, especially in parasitic forms of intracellular habitat. 

 The Mastigophora are divided into three subclasses, of which 

 the first, the Flagellata, contains the more typical forms, and con- 

 stitutes the nucleus, so to speak, of the class ; while the two remain- 

 ing subclasses, the Dinoflagellata and Cystoflagellata, may be 

 regarded as specialized offshoots of the primitive flagellate stem. 

 It is convenient, therefore, to deal with the Flagellata in a general 

 manner first, and then to describe the special features of the other 

 two subclasses. 



SUBCLASS I. : FLAGELLATA (ETJFLAGELLATA). 



General Characters. The members of this group are for the most 

 part of minute size, and seldom attain to considerable dimensions ; 

 forms of relatively large size, such as the species of Euglena and 

 allied genera, are small as compared with the larger species of the 

 Sarcodina and other classes. As a rule the Flagellata are free- 

 swimming organisms ; a certain number, however, are sedentary in 

 habit, attaching themselves to a firm basis, and using their flagella 

 for food-capture alone. There is a great tendency to colony- 

 formation in this group. In the process of multiplication by fission 

 of the ordinary type, separation between the daughter-individuals 

 may be incomplete, so that they remain connected together, either 

 by means of a common envelope, house, or gelatinous matrix, or 

 by organic, protoplasmic union, or in both ways. Repeated fission 



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