MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 255 



or girdle around the cell, giving the impression of an annular row of 

 cilia which led to the earlier name Cilioflagellata for the group 

 (Fig. 70, p. 13()). ^Multiple flagella are characteristic of the Poly- 

 mastigida and H\'permastigida. 



Nuclei for the most part are simple vesicular and endosome-bear- 

 ing nuclei, but there are wide variations in complexity so that a 

 general description is quite inadequate (see p. 56). 



Chromatophores and Stigmata. — Chromatophores are the most 

 characteristic of the plastids in this group. While usually present 

 as definite bodies of characteristic size and shape, they are sometimes 

 in the form of a vague network (Fig. 124), or as irregular clumps of 

 chlorophyll-holding substances (Chrysomonadida, Tryptomonadida) . 

 More often, however, they are definitely formed bodies, discoidal, 

 cup-shape, band-, star-, or rod-form. Their colors vary from yellow 



A 



B 



C 



D 



Fig. 124. — Flagellates with chlorophyll iu a reticulated network. .4, B, Chrynapsis 

 sagene; C, D, Chrysapsis fcncstrata. (After Pascher). 



and brown (Chrysomonadida, Cryptomonadida, Dinoflagellida) to 

 a bright green in the Phytomonadida, while blue-green and red are 

 occasionally seen. In all cases the basic color is chlorophyll-green, 

 varying in shade as it does in the higher plants ; this is often masked 

 by overlying colors which in all cases are readily dissolved out by 

 alcohol, thus exposing the typical green. 



Many of the chloroph\'lI-bearing flagellates and a few colorless 

 ones (Astasiidae) possess a minute rod-shape, oval or discoidal mass 

 of red pigmented oily (lipochrome) substance called the stigma or 

 "eye-spot," which is usually situated in the anterior end. According 

 to Fran9e, it may be accompanied by one or more paramylum bodies 

 which function as a lens system. Following Engelmann the stigma 

 is generally interpreted as a bit of protoplasm particularly sensitive 

 to light rays (see Mast, 1916, 1923). Observations are conflicting 



