THE PROTOZOA 



in flagellates like Euglena, although the production of gametes, and syngamy, 

 are well known in other flagellates. 



Other Flagellates. For convenience, the flagellates are sometimes sub- 

 divided into two groups, the plant-like and the animal-like forms. The class 

 is so heterogeneous that such a major subdivision is of questionable value. 

 Some of the plant-like forms are clearly very similar, structurally, to other 

 species which lack chlorophyll. It is evident that the Flagellata are very 

 difficult to separate from the unicellular plants, on the one hand, and from the 

 Sarcodina, on the other; they also show some affinities with the Sporozoa, to 

 be described later. The flagellates include many interesting forms (Fig. 8.11). 

 In Mastigamoeba the cell is amoeboid, although the presence of a flagellum 

 leads to its classification as a flagellate. In Peranema the cytosome is strikingly 

 mobile, and the flagellum is generally held straight out anteriorly, vibrating 

 only at the distal end as the animal progresses. In Monosiga and related 

 forms, called choanoflagellates, there is a delicate protoplasmic collar sur- 

 rounding the flagellum, and ingestion of food particles occurs in this region. 

 Noctiluca, a dinoflagellate, is one of the organisms responsible for luminescence 

 in the ocean. 



Parasitic Flagellates. Many of the Flagellata are parasitic. The lower di- 

 gestive tract of man and other mammals often harbors such forms, and almost 

 any frog or tadpole will be found to have more than one species of flagellate in 

 its large intestine. The digestive tracts of termites and wood roaches con- 

 tain an amazing array of Hypermastigicia, a group of flagellates with very 

 numerous flagella (Fig. 8.12), which have been shown to perform an essential 

 function in the digestion of wood by these insects; hence, these are not 

 actually parasites in the accepted sense. 



The forms called trypanosomes ("awl body") occur in the blood of verte- 

 brates and the digestive tracts of invertebrates (Fig. 8.13). A trypanosome 



Fig. 8.12. A hypermastigote flagellate, 

 7 richonympha campanula, from the alimentary 

 tract of a termite. The longitudinal striae 

 represent the lines of attachment of additional 

 hundreds of flagella, with which the anterior 

 portion of the organism is completely covered. 

 (Adapted from C. A. Kofoid and O. Swezy, 

 1919, University of California Publications in 

 ^oology, vol. 20, printed by permission of 

 the University of California Press.) 



243 



