270 THE PROTOZOA 



Suborder 2 : Holomastigina. With numerous flagella radiating from a 

 spherical or approximately spherical body. 



This suborder contains the single genus MulticHia, Cienkowski, to which 

 several species, some fresh-water, some marine, have been referred. The 

 number of flagella varies in different species, and their precise relation 

 to the nuclear apparatus remains to be made out. M. lacustris, Lauterborn 

 (Fig. 113, A), is multinucleate ; M. palustris, Pe"nard (Pig. 113, B), has a single 

 nucleus. The body is not covered by a cuticle, and may throw out pseudo- 

 podia, or even become amoeboid (Lauterborn). Nothing is known of the 

 life-cycle, but in M. lacustris Lauterborn observed reproduction by simple 

 fission (plasmotomy ?). In the present state of our knowledge adequate data 

 are lacking for discussion or the affinities of this genus. Doflein (7) regards 

 it as a form lying at the root of the Infusorian stem, and derives the most 

 primitive Ciliata from a form similar to Midticilia, in which the numerous 

 flagella become specialized in structure and movement to give rise to an even 

 coat of cilia ; Peiiard (302), on the other hand, considers Multicilia allied to 

 the Heliozoa (p. 249). It is clear that the genus is one which would repay 

 further study. 



ORDER II. : PBOTOMONADINA. Flagellates for the most part of small or 

 minute size ; with a single flagellum ; or with a principal and one or two acces- 

 sory flagella ; or with two flagella, one directed anteriorly, the other pos- 

 teriorly as a trailing flagellum. Nutrition holozoic, saprophytic, or parasitic ; 

 in the first case the food-particles are ingested at the base of the flagellum, 

 where a definite mouth-opening may be present or absent, but without a 

 distinct oesophagus in any case. The contractile vacuole is generally single, 

 if present, and empties itself direct to the exterior. 



This order .comprises a vast assemblage of genera and species, subdivided 

 by Doflein into eight families, one of which, the Trypanosomidce, including 

 the important parasitic genus Trypanosoma, is discussed in detail in the next 

 chapter. The cuticle is generally thin, and the body is often capable of 

 amoeboid or metabolic movements ; if amoeboid, however, the flagellum is 

 the organ of locomotion, so long as it is present, and not the pseudopodia. 

 The relations of the flagellum to the nuclear apparatus are, in general, of the 

 second type (p. 263), according to Hartmann and Chagas (62) that is to say, 

 with distinct centrosome and blepharoplast ; but it is extremely probable 

 that in the simpler forms Type 1 occurs also (compare Alexeieff, 327), and in 

 the Trypanosomidoe the distinctive feature is the possession of Type 3, with 

 trophonucleus and kinetonucleus, as also in some of the Bodonidce (Prowa- 

 zekia). The life-cycle of the free-living forms is probably in general of a 

 simple type, similar to that described above in Copromonas (Fig. Ill) ; but 

 observations on the sexual processes are at present very scanty. 



For a detailed description of the forms included in this order the reader 

 must be referred to the larger treatises, especially Biitschli (2) and Senn (320) ; 

 it must suffice here to mention some of the more typical forms. Cercomonas, 

 type of the family Cercomonadidce (Fig. 114), has a single flagellum ; the hinder 

 end is frequently drawn out into a long tail-like process, and is capable of 

 change of form. (Ecomonas (Oikomonas) differs in having the body rounded. 



Monas, type of the family Monadidos, has a principal flagellum and one 

 or two accessory flagella. Cladomonas and Spongomonas (Figs. 41, 42) form 

 arborescent colonies ; the constituent monads have two flagella of equal 

 size, both directed forwards. Alexeieff (327) considers that the Monadidce 

 should be placed in the suborder Chrysomonadina (see below). 



Bodo (Fig. 115), type of the family Bodonidce, has two flagella, one directed 

 forwards, the other backwards as a trailing flagellum ; the species of this 

 genus are free-swimming and do not form colonies ; they occur both free- 

 living and parasitic, for the most part in the digestive tracts of various animals. 

 Bodo lacertcs, from the cloaca of Lacerta spp., has been studied by Prowazek 

 (354), who has described a process of autogamy, but doubt has been cast upon 

 his observations by Dobell (336). Note also the occurrence of Bodo-liko 

 forms in the development of Gryptodifflngiq, (p. 230, supra). The flagellate 



