The Trypanoplasmae flourish in the blood and intestines of many fishes as well as in the intestines of many invertebrates; it is not yet certain whether any of them are pathogenic. All para sitic Herpetomonadina feed osmotically. The group is unicellular and uninucleate, and reproduction is by simple or occasionally by multiple division. Sexual processes are unknown.
Another important family of the Protomonadina that must be mentioned is the Craspedomonadidae ; it consists of free-living, unicellular, heterotrophic flagellates ; they have a delicate collar around the flagella. They are unicellular and uninucleate. Repro duction by simple division, fertilization unknown. Important types : Codosiga, Salpingoeca.
8. Order Polymastigina. Flagellates, parasitic and "eating," with a very characteristic division of the nucleus. The lower forms (trichomonads) have 2-5 flagella, the higher (hypermasti gina) have often several hundred. All are innocuous intestinal parasites of vertebrates, including man, and of insects. The Trichonymphidae are symbiotic with the wood eating termites (see above). The Polymastigina are unicellular and usually uni nucleate; only a few of the higher forms such as Calonympha are multinucleate. Reproduction is by simple fission, no sexual proc ess being known. Important types: Trichomonas (T. intestinalis is a harmless intestinal parasite of man, T. buccalis lives in the tooth-insertion of. man), Trichonympha.
9. Order Distomatina. Heterotrophic, free-living and eating liv ing organisms or parasitic; they have the appearance of two flagellates stuck together. They have two nuclei and two flagellar apparatuses. Reproduction is by simple fission; fertilization processes are unknown. Important type : Giardia, an intestinal parasite (probably innocuous) of man and many other mammals.
I. Order Amoebina. Rhizopoda that have amoeboid movement, i.e., they travel by means of broad pseudopodia produced over the whole body surface. This group is as unnatural as the class Rhi zopoda (see above). The amoebae were for a short time regarded
as the most primitive, because structurally the simplest, of living organisms. Nowadays this view is not held. We know, for instance, that certain Chrysomonadae are definitely without flagella and show amoeboid movement; they are amoebae. Yet in every other character they are typical Chrysomonadae. It is therefore entirely reasonable to imagine that many amoebae are extreme secondarily altered forms of the other groups of Protozoa.
All amoebae are heterotrophic and feed on living organisms; many are free-living, in fresh water, sea water and soil; some are parasitic, as a rule in the gut. They are entirely unicellular and for the most part uninucleate. Reproduction is by simple fission or multiple division in cysts (Entamoeba fig. 21). Fertilization processes are known only in very few species. The amoebae are divided according to their method of nuclear division. Important types :—IV ahlkampfia (fig. 15) and Hartmanella (free-living, feeding on bacteria), Amoeba proteus (living in water), Enta moeba histolytica (fig. 21), the cause of amoebic dysentery of man, Entamoeba coli, an innocuous gut-parasite of man, Enta moeba gingivalis, a parasite, possibly harmless, of the slime cover ing the tooth-bases of man. (See also AMOEBA.) 2. Order Thecamoebina. Free-living Rhizopoda whose bodies are surrounded by a cup- or flask-shaped shell. Pseudopodia are extruded from the opening in the shell. Characteristic also is the presence of layers or zones of protoplasm which stain deeply with the so-called nuclear stains, and are therefore described as chromidia (see above). The shell may be composed either of a protoplasmic skin or of "pseudochitin" or of plates of silica, produced by the animal itself (Euglypha), or of foreign bodies picked up by it as it goes along and saved for the purpose (Diifiugia). The group is entirely unicellular and as a rule uninucleate. Reproduction is by simple fission, or, in the hard shelled forms, characteristically by gemmation. The mother indi vidual extrudes a portion of its protoplasm from its aperture and this grows a new shell. In the "wall-building" forms the "building materials" accumulated by the mother-animal pass to the surface of the gemma; only then does a daughter-nucleus from the newly divided mother-nucleus wander into the gemma, which then becomes free. Fertilization is unknown in this order.