FLAGELLATA I 1 5 



An undulating membrane occurs, sometimes passing into the 

 flagellum in certain genera, all parasitic, such as Trypanosoma 

 (incl. Hcrpetomonas), Trichomonas, Hexamitus, and JJinenympha. 



In some cases the flagellum (or flagella) is inserted into a 

 definite pit, which in allied forms is the mouth-opening. The 

 contractile vacuole is present in the fresh-water forms, but not 

 in all the marine ones, nor in the endoparasites. It may be 

 single or surrounded by a ring of minute " formative " vacuoles 

 or discharge into a permanently visible " reservoir." This again 

 may discharge directly to the surface or through the pit or canal 

 in which the flagellum takes origin {Euglena). 



The " chromatophore " may be a single or double plate, or 

 multiple.-' In the peculiar form Paramoeba the chromatophore may 

 degenerate and be reproduced anew. It often encloses rounded or 

 polygonal granules of uncoloured plasma, very refractive, known 

 as " pyrenoids." These, like the chromatophores, multiply by direct 

 fission. The "reserves" maybe (1) fat-globules; (2) granules of 

 a possibly proteid substance termed " leucosin"; (3) a carbohydrate 

 termed "paramylum," differing slightly from starch (see p. 95); 

 (4) true starch, which is usually deposited in minute granules to 

 form an investment for the pyrenoid when such is present. 



A strongly staining granule is usually present in the plasma 

 near the base of the flagellum. This we may term a "blepharo- 

 plast " or a " centrosome " in the wider sense. 



Fission is usually longitudinal in the active state ; a 

 few exceptions are recorded. Encystment is not uncommon ; 

 and in the coloured forms the cyst - wall is of cellulose. 

 Division in the cyst is usually multiple;^ in the coloured 

 forms, however, vegetative growth often alternates with 

 division, giving rise to plant-like bodies. Polytoma and other 

 Chlamydomonadidae multiply by "brood-formation" in the 

 active state; the blepharoplast, as Dangeard suggests, persist- 

 ing to continue the motion of the flagella of the parent, while 

 the rest of the plasm divides to form the brood. Conjugation 

 has been observed in many species. In some species of 

 Chlamydomonas it takes place after one or both of the two 



1 The colouring matter is chlorophyll or some allied colouring matter. In the 

 jellow and brown forms the additional pigment is termed loosely "diatomin," 

 but its identity with that of Diatoms is in no case proved. 



2 Notably in the Craspedomonadidae, where transverse division also occurs. See 

 Baoul Franc^, Die Craspedomonadineen (Buda-Pesth, 1897). 



