MASTIGOPHORA 



331 



^The periplast in the heteromastigotes may be drawn out into an 

 undulating membrane which helps locomotion. 



When the periplast is thin or absent the body-form may still 

 be preserved by an internal stiff rod — as, for example, the axostyle 

 of Trichomonas. 



There is a difference of opinion as to which is the anterior end of 

 the mastigote. We believe, with Sambon, that the non- flagellate 

 end should correctly be considered as the anterior end, but several 

 authorities hold quite different 

 views, and our anterior end 

 will correspond with many 

 other writers' posterior. Very 

 often there is a depression 

 somewhere on the surface of 

 the animal, generally near the 

 base of the flagellum, which is 

 intended for the reception of 

 food, and is called the mouth 

 or cytostome; more rarely there 

 is an oesophagus leading into 

 the interior of the cell. Nutri- 

 tion may be holozoic or holo- 

 phytic, but this hardly concerns 

 us, as the forms to be described 

 are all parasitic, and live in 

 fluids from which they absorb 

 nourishment by their whole 

 surface. 



In the cytoplasm there is a 

 nucleus, and in certain forms 

 two nuclei: a trophonucleus for 

 nutrition, and a kinetonucleus 

 for movement. The character 

 of these nuclei will be dealt 

 with in detail in the section 

 Trypanosomidse. The cyto- 

 plasm may also contain food 

 vacuoles, contractile vacuoles, 

 chromatin particles, and meta- 

 plastic granules. 



Life-History. — Reproduction takes place asexually by simple 

 division. Latent or encysted forms are also known. 



The whole subject of the structure and life-history of the parasitic 

 Mastigophora requires much further research, which, indeed, is 

 being rapidly carried out all over the world — in fact, so rapidly that 

 it is hardly possible to write anything on the subject as a whole which 

 will not quickly be out of date. 



Classification.- — ^The Mastigophora may be divided into subclasses 

 as follows: — 



Fig. 67. — Diagram of the Life- 

 Cycles OF A Mastigote {Copro- 

 monas suhtilis Dobell) . 



The upper cycle demonstrates simple 

 fission and the lower sporogony. 



(After Dobell, from the Quarterly 

 Journal of Microscopical Science.) 



