SARCODINA , a
See also:group or phylum of
See also:Protista, defined by O . Butschli as those which during their active and motile existence
See also:discharge the functions of motion and
See also:nutrition by
See also:simple flowing movements of their
See also:protoplasm or by the extension of simple pseudopods, which
See also:merge without trace into the protoplasmic
See also:body (
See also:Bronn's Tierreich, vol. i. pt. i., 1882) . Thus defined, it is co-extensive with the older group
See also:Rhizopoda (Dujardin), and comprises five classes: Proteomyxa (Lankester), Rhizopoda (Dujardin),
See also:Foraminifera (d'
See also:Heliozoa (
See also:Haeckel) and
See also:Radiolaria (Haeckel) . The delimitation of Sarcodina is not unattended with difficulties . A very few of those we include possess in addition to the pseudo-pods one or more flagella, such as Dimorpha and Myriophrys (Heliozoa), Arcuothrix (Rhizopoda), and might equally be referred to the
See also:Flagellata (q.v.) . The
See also:Sporozoa differ in that their active state is usually (not always, e.g .
See also:Haemosporidia, &c.) a wriggling, sickle-shaped
See also:cell, that growth takes place in the whole
See also:surface of the body, and not by ingestion of
See also:food and consequently without the active deformations that characterize Sarcodina, and that the
See also:life-cycle embraces at least two alternating modes of brood formation . The subdivision of the phylum is no less difficult . The character of the pseudopods (see
See also:AMOEBA) is the most obvious one to select, as it appears to be fairly
See also:constant . The surface may be a " precipitation-pellicle," not wetted by
See also:water, and the cytoplasm immediately within (" ectosarc ")
See also:free from granules, so that no streaming
See also:movement is visible at the surface of the pseudopods, which are blunt or taper sharply to a point (Rhizopoda Lobosa); or the cytoplasm has no such protective
See also:outer layer, and the granules extend to the surface where they show a constant streaming, and the pseudopods are
See also:fine-pointed, and taper very slowly to the tip, as in all the other groups . For convenience, however, from general similarity of
See also:habit, habitat and general structure, we have been obliged to give a minor importance to this character within Rhizopoda . The divisions then stand thus: I .
PROTEOMYXA.—Pseudopods fine granular, not branching freely; fission usually multiple, in a cyst; no conjugation
See also:process known . 2 . RHIZOPODA.—Simple forms, sometimes with a simple
See also:shell, chitinous, siliceous or of cemented particles, never calcareous; pseudopods lobose, in the tapering and branching never either stiff or reticulate . 3 . HELIOzoA.—Pseudopods granular, finely radiate, and gradually tapering, stiff ;
See also:skeleton variable, never calcareous nor of cemented particles . 4 . FoRAMINIFERA.—Pseudopods branching freely and anastomosing, flexible except in a few pelagic forms where they are more radiate; shell variable, mostly of cemented sand-grains, calcareous, very rarely siliceous in a few deep-
See also:sea forms, not generically separable from 5 . RADIOLARIA.—Cytoplasm divided into a central and a peripheral region by a perforated membranous central capsule; pseudo-pods radiate flexible branching or not; skeleton either of a proteid (?) substance (" a canthin ") or siliceous, of spicules or forming an elegant lattice, more rarely continuous . 6 .
See also:LABYRINTHULIDEA.--Body a reticulate plasmodium, formed by cells more or less coalescent, and connected by a network of anastomosing threadlike pseudopods . Cells aggregated into loose networks without distinct boundaries, the minor aggregates connected by fine threadlike pseudopodia . 7 .
MYxOMYCETES.—Cells at first free, finally aggregated to
See also:form a coalescent fructification, usually preceded by a continuous or fenestrated plasmodium stage in which all cytoplasmic boundaries may be lost . The
See also:reproduction processes of the Sarcodina are (I) Binary fission, equal or nearly so . (2) Multiple fission or " sporulation " (also termed " brood formation ") . Conjugation (equal or unequal) usually occurs between cells produced by the latter mode (microgametes) ; or if not, there are antecedent processes suggesting that brood formation has been lost . Conjugation is entirely unknown in Proteomyxa, Labyrinthulidea and Myxomycetes, even at stages where it occurs in other groups, and it has only been definitely made out in a very limited number of genera in the remaining groups . The zygote or product of cell
See also:fusion is usually here, as in the majority of types of conjugation, a resting cell . (See the
See also:separate articles on the classes.) The
See also:young of the Sarcodina, formed from' the outcome of multiple fission, or single resting cells (spores), may be provided with pseudopodia from the first (myxopods or amoebulae), or come into active life for a
See also:time with flagella (mastigopods or flagellulae) . (M .
SARCOCARP (Gr. aapE, flesh, Kaplros, fruit)
SARCOPHAGUS (Gr. vapsorg yos, literally " flesh-eat...
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