MYCETOZOA AXD GEEGARiy^ Sol 



Such as these are associated together in groups, like colonies, on various plans ; and the constituent 

 members of the compound mass undergo changes leading to the production of new Amoeboid and 

 other forms. Such minute flagellate organisms, together with simple protoplasm, make up for the 

 most part the living slime of Sponges. 



There are also some small organisms, similar at one time of their developmental growth to little 

 puff-balls and other fungi, and parasitic on plants and wood, which break up and allow iunumerable 

 spores to escape ; and each of these gives rise to a flagellate Monad, with nucleus and contractile 

 vesicle, and endowed witli power of enclosing and feeding on organic atoms. These Monads, 

 becoming Amoebas, join together, and form a large jelly-like mass (" plasmodium "), in which 

 ultimately the fungoid organisms and their spores are developed in their turn. This general 

 or common slime colony, in the meantime, pushes out pseudopods, moves on and on, engulfing 

 food-particles, and, when extended to the utmost, becomes a coarse network, showing the usual 

 circulation (pseudo-cijdosis, Wallich) of granules in the sarcode. These are the Mycetozoa alluded to 

 above.* The Labyrinthulea is such a marine Protozoan. It forms groups of numerous yellowish 

 nucleated corpuscles, usually spindle-shaped, but changeable, very loosely associated together in a 

 net-like tissue, and gliding about within its substance. Some free Amceboids are given off at times 

 by the tissue ; but the tapering corpuscles by-and-by mass themselves in groups ; these become 

 encysted, and at last each corpuscle, or gelatinous cell, produces four young cells, or spores. 



L. The Jfagospficera, a small spherical body rolling through the water (salt and fresh), consists 

 of numerous vase-shaped nucleated corpuscles fitted together side by side, radiating from the centre, 

 with six-sided outlines, the tapering ends inwards, whilst their outer ends have vibrating fringes, 

 giving a hairy surface to the living ball. Its component cells break up and produce isolated 

 swimming atoms, and these become creeping Amoeboids. Each of these, in an encysted condition, 

 divides again and again, until a new compound Magosphere is formed, which breaks the wall and 

 escapes. 



LI. Another life-history of one of the Protozoa, although not that of one of the Ehizopods, 

 is very interesting, and shows us how close is the relationship, and how narrow are the boundaries, 

 between the Protista and the Protozoa proper, and between their several groups. The minute parasites 

 found in the insides of worms and insects, and known as Gregarince, have been closely studied. 

 In its advanced stage of growth a Gregarina consists of one, two, or three cell-like, nucleated 

 corpuscles of contractile protoplasm, enclosed in a soft, smooth, elastic skin, sometimes furnished with 

 hooks at one end. The "nucleus" is large, mostly round and clear, with a "nucleolus." By 

 contractions of the sarcode just beneath the skin, the Gregarina moves creepingly along on the moist 

 surfaces from which it absorbs its nutriment. Reproduction takes place either by division or by 

 zoospores. The latter are produced after a "resting stage," when either a single individual, or 

 several together, have become " encysted ; " and, the nuclei disappearing, the sarcode has broken up 

 into a great number of germinative cells, or spores, called Pseudo-naviculse. From each of these 

 an Amceboid or Montron escapes, which becomes nucleated, and is transformed into an Amoeba ; and 

 this, furnished with an envelope, lives as a Gregarina. 



LII. Like other very minute animalcules, mouthless, but otherwise resembling Infusoria to 

 some extent, the exceedingly small moving bodies seen (with high microscopic power) in decomposing 

 organic infusions of organic substances, and known as Bacteria and Vibriones, are grouped among the 

 Monera. They look like delicate tremulous filaments, and may be straight, curved, or spiral, 

 oscillating, vibrating, or undulating, and are often jointed, or partially divided in the process of 

 being multiplied by " fission.*' 



LIU. One interesting fact is observable in the comparison of the life-history of Ehizopods with 

 that of higher animals even with the highest of the Vertebrata. The organic material which is their 

 only living substance, excepting some occasional mechanical support derived from mineral matter, is 

 really a most essential, if not, indeed, in some respects the most essential, substance in even our own 

 bodily system. As the sensitive copper wire in the electric cable is the essential portion of that 

 wonderful cord, so the delicate innermost protoplasmic core of our complex nerve-chord and 

 nerve-threads is essential to the perfection of our nerve-system. In some of the lower animals, 

 * See also W. S. Kent, "Pop. Sci. Rev.," n.s., No. 18, 1881, p. 97, &c. 



