Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/864

Rh 840 PROTOZOA [PROTEOMYXA. doubt is justified in regard to Haeckel s Protamaba primitiva, which was observed by him in pond water and differs from Protogenea in having lobose pseudopodia, whilst agreeing with it in absence of nuclei contractile vacuoles, and other differentiation of structure. 12 IG. II. Various Proteomyxa. 1. Protomyra aurantiaca, Ilacckcl, plas- lium phase. The naked protoplasm shows branched, vtticulate processes (pMudopodla), andnnmeroiu non-contrac;i1e vacuoles. it is in the act of en- RUlphlng a Ceratium. Shells of engulphed Ciliata (Tintimialjula) are embedded eeply in tlie protoplasm a. 2. Cyst phase of I rotomyxa. a, transparent cvst- wall ; b, protoplasm btok n up into spores, a. Flagellula phase of Protomyxa form assiui.el by the spires on their escape from the cyst. 4. Amoebula f the same, the form assumed after a short period by the flagcllulse 5 rampyrella tpiroyyr.e, Cienk., amoeba phase penetrating a cell of Spirogyra b jy a proc.-ss of its protoplasm r, and taking up the substance of the Splroeyra Tell, some of which is seen within the Vampyrella a. C. Large individual of ampyrt-lla, showing pseudopodia f, anil food panicles a. The nucleus (though present) Is not shown in this d, awing. 7. Cyst phase of Vampvrella. The
 * nt of the cyst have divided into four equal parts, i.f whMi three are
 * is commencing to break its way through the cyst-wall f; a, food

. ArchertM IMtoui, Unkestcr, showing lobose and fi lamentrms rotoplasm, and three groups ,,f chl-rophyll corpuscles. The protoplasm g is engulphmg a Bacterium t. 9. Cyst phase of Archerimi. a, spinous cvsr-wall 6, greei.-colourcd contents. 10. Chlorophyll corpuscle of Aivhcrina showing etrasctnst.c dmsion. 11. Actinophryd form of Archerina. 6, chlorophvll coi- 3. Protognei primontialiK, H.icckel (Amceba porrecta, M. Scliultze) irom Scnultze figure. The structureless protoplasmic network described by Hacckcl from spirit-preserved specimens of Atlantic ooze and identified by him with Huxley s (28) Batliybius, as also the similar network described by Bessels (29) as Protobathybius, must be regarded for the present as insufficiently known. It is possible that these appearances observed in the ooze dredged from great depths in the Atlantic are really due to simple Protozoa. On the other hand it has been asserted by Sir Wyville Thomson, who at one time believed in the independent organic nature of Bathybius, that the substance taken for protoplasm by both Huxley and Haeckel is in reality a gelatinous precipitate of calcium sulphate thrown down by the action of alcohol upon sea-water. Other naturalists have pointed to the possibility of the protoplasmic network which Bessels studied in the living condition on board ship being detached portions of the protoplasm of Reticularia and Radiolaria. The matter is one which requires further investigation. Archerina Boltoni is the name given by Lankester (14) to a very simple Gynmomyxon inhabiting freshwater ponds in company with Desmids and other simple green Alga 1. (Fig. II. 8 to 11). Archerina exhibits an amoeba phase in which the protoplasm is thrown into long stiff filaments (Fig. II. 11), surrounding a spherical central mass about ^uV-jjth inch in diameter (actinophryu form). A large vacuole (non-contractile) is present, or two or three small ones. No nucleus can be detected by careful use of reagents in this or other phases. The protoplasm has been seen to ingest solid food particles (Bacteria) and to assume a lobose form. The most striking characteristic of Archerina is the possession of chlorophyll corpuscles. In the actinophryd form two oval green-coloured bodies (b, b) are seen. As the protoplasm increases by nutrition the chlorophyll corpuscles multiply by quaternary division (Fig. 11. 10) and form groups of lour or of four sets of four symmetrically arranged. The division of the chlorophyll corpuscles is not necessarily followed by that of the protoplasm, and accordingly specimens are found with many chlorophyll corpuscles embedded in a large growth of protoplasm (Fig. II. 8) ; the growth may increase to a considerable size, numbering some hundreds of chlorophyll corpuscles, and a proportionate development of protoplasm. Such a growth is not a plasmodium, that is to say, is not formed by fusion of independent amoeba forms, but is due to continuous growth. When nutrition fails the individual chlorophyll corpuscles separate, each carrying with it an investment of protoplasm, and then each such amoeba form forms a cyst around itself which is covered with short spines (Fig. II. 9). The cysts are not known to give rise to spores, but appear to be merely hypnocysts. The domination of the protoplasm by the chlorophyll corpuscles is very remarkable and unlike anything known in any other organism. Possibly the chlorophyll corpuscles are to be regarded as nuclei, since it is known that there are distinct points of affinity between the dense protoplasm of ordinary nuclei and the similarly dense protoplasm of normal chlorophyll corpuscles. CLASS II. MYCETOZOA, De Bury. Characters. Gymnornyxa which, as an exception to all other Protozoa, are not inhabitants of water but occur on damp surfaces exposed to the air. They arc never parasitic, as are some of the Proteomyxa most nearly allied to them (Plasmodiophora, &c.), but feed on organic debris. They are structurally characterized by the fact that the amoeba forms, which develop either directly or through flagellulffl from their spores, always form large, sometimes very large, i.e., of several square inches area, fusion plasmodia (or rarely aggregation plasmodia), and that the spores are always chlamydospores (i.e., provided with a coat) and are formed either in naked groups of definite shape (sori) or on the surface of peculiar columns (conidiophors) or in large fruit-like cysts hich enclose the whole or a part of the plasmodium and develop besides the spores definite sustentacular structures (capillitium) holding the spores in a mesh-work. Three orders of Mycetozoa are distinguishable according to the arrangement of the spores in more or less complex spore-fruits. ORDER 1. SOROPHORA, Zopf. Characters. My cetozoa which never exhibit a vibratile (monadi- form) swarrnspore or flagellula phase, but hatch from the spore as amoebae. A true fusion plasmodium is not formed, but an aggrega- gation plasmodium by the contact without fusion of numerous amoeba forms. The spore fruit is a naked aggregation of definitely arranged encysted amoeba; called a sorus, not enclosed in a common capsule ; each encysted amceba has the value of a single spore and sets free on germination a single amtebula. They inhabit the dung of various animals. Genera. Copromyxa, Zopf ; Cynthnlina, Cienk. ; Diclyostelium, Brefeld ; Acrasis, Van Tieghem ; Polyspondylium, Brefeld. ORDER 2. ENDOSPOREA, Zopf. Characters. Mycetozoa always passing through the flagellula phase and always forming true plasmodia by fusion of amceba forms. The spore-fruit is in the form of a large cyst which encloses a quantity of the plasmodium ; the latter then breaks up into (a)