PROTOZOA: MONERA. 6 1 



CHAPTER II. 

 RHIZOPODA. 



GENERAL CHARACTERS OF THE RHIZOPODA. The Rhizopoda 

 may be defined as Protozoa which are destitute of a mouth^ are 

 simple or compound, and possess the power of emitting "pseudo- 

 podia" They are mostly small, but some of the composite 

 forms, such as the sponges, may attain a very considerable 

 size. Structurally, a typical Rhizopod as an Amoeba is 

 composed of almost structureless sarcode, without any organs 

 appropriated to the function of digestion, and possessing the 

 power of throwing out processes of its substance so as to con- 

 stitute adventitious limbs. These are termed " pseudopodia," 

 or false feet, and are usually protrusible at will from different 

 parts of the body, into the substance of which they again 

 melt when they are retracted. They are merely filaments of 

 sarcode, sometimes very delicate and of considerable length, 

 at other times more like finger-shaped processes ; and they 

 are identical with the little processes which can be thrown 

 out by the white corpuscles of the blood and by pus-cells. 

 Indeed, it has been remarked by Huxley that an Amoeba is 

 structurally "a mere colourless blood-corpuscle, leading an 

 independent life." 



The class Rhizopoda is divided into five orders viz., the 

 Monera, the Amdbea, the Forammifera, the Radiolaria, and 

 the Spongida, of which the last is occasionally considered as a 

 separate class, or is removed entirely from the Protozoa. 



ORDER I. MONERA. This name has been proposed by 

 Haeckel for certain singular organisms which may provisionally 

 be regarded as the lowest group of the Rhizopoda. They are 

 very minute in size, and are distinguished by the fact that 

 the body is composed of structureless sarcode, capable of emit- 

 ting thread-like prolongations or pseudopodia, but destitute 

 of either nucleus or contractile vesicle. The pseudopodia are 

 mostly in the form of delicate filamentous processes of sarcode, 

 which exhibit a circulation of minute molecules and granules 

 in their interior and along their edges. Sometimes the pseu- 

 dopodia may be simple, as in Protamceba (fig. 7, a), or they 

 may be ramified and anastomosing, as in Protogenes. The 

 form of the body, though very mutable, may be simple ; or 

 the organism may form a kind of colony of protoplasmic 

 masses united by their interlacing pseudopodia (as in Myxo- 



