286 ORDER: PROTOMONADIDA 



into a cylindrical collar or cuff around the base of the flagelluni. The 

 majority of flagellates belonging to the Protomonadida are free-swimming, 

 but some of them develop attachment filaments, and it is in these forms 

 that cup-like sheaths (loricse) and collars commonly occur. 



This order includes a large number of free, non-parasitic, and coprozoic 

 forms, as well as certain parasites such as the trypanosomes and some of the 

 intestinal flagellates of man and animals. 



Many of the simpler Protomonadida are able to ingest solid food at any 

 part of the body surface by means of pseudopodia, just as amoebae do. 

 These forms are sometimes known as the Pantostomatina.. Others, 

 however, only ingest food near the base of the flagellum, where a permanent 

 cytostome may or may not be present. In the case of the parasitic 

 blood-inhabiting Trypanosomidae and the Cryptobiidse there is no 

 cytostome, and nutrition is effected by the absorption of nutrient material 

 from the blood in solution. In some saprophytic forms it is probable that 

 both solid food is ingested as well as nutriment in a soluble form. The 

 Protomonadida do not, as a rule, possess any accessory internal organs, 

 but in some of them axostyles, parabasals, supporting filaments and other 

 structures are developed. 



The order PROTOMONADIDA may be subdivided into two sub-orders, the 

 Eumonadea, which are free-swimming forms, and the Craspedomonadea, 

 which possess attachment organs, and which may or may not have collars 

 or loricse. 



(1). Stib-Order : Eumonadea. 

 The members of this sub-order are flagellates of relatively simple 

 structure which have one or a small number of flagella. Each flagellum 

 arises from a blepharoplast, which may be on the nuclear membrane or 

 separate from it. When more than one flagellum is present, one may 

 function as a trailing flagellum. Accessory structures such as axostyles 

 are sometimes present. The following families may be recognized: 



1. Family: MONADID^ Kent, 1880. — Flagellates of simple structure with 

 one or more free flagella, the axonemes of which originate in blepharo- 

 plasts which are either upon the nuclear membrane or removed from it. 

 When there is more than one flagellum, one may function as a trailing 

 flagellum. The body, which is very metabolic, may or may not be pro- 

 vided with a cytostome. 



2. Family: TRYPANOSOMiD.'E Doflein, 1901. — Flagellates which have a 

 single flagellum and are parasitic in vertebrates, invertebrates, or plants. 

 The body is usually elongate, and the axoneme of the flagellum in its course 

 from the blepharoplast to the point of origin of the flagellum may, if the 

 blepharoplast be near the nucleus or posterior to it, pass along the border 



