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THE RHIZOPODA. 



The Rhizopods Appearance Protoplasm or Sarcocle Its Character and Functions The "Contractile Vesicle" Amoeba 

 and Moncru True " Cells "Assimilation of Food Contents of the Endosarc The " Vacuoles " Food of the 

 Amoeba Naked Lobose Rhizopods Shelled Lobose Rhizopods Sun-animalcules Actinopkryt sot The Radiolaria 

 The Polycistina The Reticularia The Foraminifera Imperf orate or Porcellanous Foraminifera Perforate or 

 Vitreous "Forams" The Flagellata Gregarina; The Link Connecting the Rhizopods and Vertebrates Bibliography 

 Classification. 



I. AMONG the minute animals which escape our naked sight, but may be seen by the aid of a 

 magnifying glass in some instances, but often only under the far stronger lenses of the microscope, 

 are those which are known as Rhizopoda,* or Myxopoda.f 



They have, in a great degree, the same simple constitution as several other kinds of animalcules 

 which are grouped by naturalists as Protozoa, J such as Infusoria (also Sponges), their essential living 

 material being merely a structureless and jelly-like or mucous substance ; and thus they stand as the 

 first in the scale of animal organisation, as it rises from the most simple to the more highly 

 organised animals with their manifold tissues and complicated structures. 



II. The delicate albuminous material of the Rhizopods and their allies is a "semi-fluid, 

 nitrogenous, formative substance," termed " Protoplasm," || as being the simplest or first life-matter 

 known to us. It is also called "Sarcode," IT as supplying the place of flesh, rather than being flesh- 

 like itself. It is probably composed of carbon, hydrogen, oxygen, and nitrogen, like some other 

 organic compounds ; and it is the physical basis of life in both animals and vegetables. 



This slimy, white-of-egg-like sarcode of the Rhizopods, though granular, with exceedingly fine 

 particles, and to some extent differentiated by local formation of special groups of granules, known 

 by some as " Endoplasts,"** shows no definite parts or divisions of a body such as characterise higher 

 animals ; nor has it permanent limbs, nor body -cavity, nor alimentary canal, nor nerves, nor blood. 

 Nevertheless, it serves for and fulfils all the necessary actions and processes of life. 



Its outer portion is generally distinguishable from the interior, and is sometimes toughened into 

 a kind of membrane, or hardened with mineral matter into a shelly coat, or a stiff skeleton of 

 network. 



More especially this corpuscle of sarcode has in itself a particular kind of motive plasticity, 

 whereby it can advance with a slowly-flowing movement of all or a part of its substance. In the 

 latter case, the elongated portions, whether thick or thin, are termed "Pseudopodia."tt 



The constituent atoms or granules, moreover, in their glairy slime, are mutually, if not equally, 

 engaged in the functions of movement and of assimilation of nutriment, and in the multiplication or 

 reproduction of individuals. In the active animal they seem to flow in a kind of circulation through 

 the little mass, and along the protruded lobes or threads ; and in many cases form special aggregations of 

 granules, or endoplasts. The smaller of these are termed "Sarcoblasts,"JJ and may be regarded as 

 ovules, or little eggs, formed within the parent, and when free, by escape or by emission, becoming 

 new little beings like the parent. A larger endoplast constitutes the "Nucleus," in the middle of 

 the animalcule. This internal corpuscle seems to be essential to the economy of most of the Protozoa, 

 forming, as it were, a starting-point of one kind of germination ; and it is the first representative 

 of a permanent vital organ. 



Another prototype or forerunner of more highly constituted organs is a minute bladder-like 

 collection of clear fluid, which in some part or other of the body, but generally towards the hinder 

 end, is seen to increase slowly to fulness ; then, suddenly contracting, to collapse and become empty, 

 at almost regular intervals of time. This " Contractile Vesicle " seems to be analogous to, if not really, 

 an organ of secretion and distribution. 



* Greek, rkiza, a root ; pous, a foot. t Greek, myxa, mucus ; pom, a foot. 



J Greek, protos, first ; zwn, an animal. 



So called from having been first found in infusions of hay and other vegetable matters. But many of the little 

 creatures first grouped under the name have been separated off, and the Infusoria are special protozoan animalcules. 

 f| Greek, protos, first ; plasma, a formation, from plasso, I shape or mould. 



T Greek, sarx, flesh ; eidos, form or appearance. ** Greek, cndon, within ; plastos, formed or moulded, 



tt Greek, pseudos, false ; pous (podog), a foot. JJ Greek, sarx, flesh ; blastof, a germ. 



