CHAPTER II. 

 RHIZOPODA. 



THE next class of the Protozoa which we have to consider 

 comprises the most characteristic and typical forms of the 

 whole sub-kingdom. The name of Rhizopoda, or " root- 

 footed " animalcules (from the Greek, rhiza, root ; and podes, 

 feet), is derived from the fact that they all possess the power 

 of throwing out at will from various parts of the body the 

 processes of sarcode which have been already spoken of as 

 pseudopodia, and by which they both move and obtain food. 

 In fact, the Rhizopoda may be shortly defined as Protozoa 

 which have no mouth and possess the power of giving out 

 pseudopodia. The pseudopodia vary a good deal in shape 

 and in other characters in different orders of the Rhizopoda, 

 but they have invariably the character of being nothing more 

 than temporary threads or finger-like processes of sarcode, 

 which can be thrust out at will, and which melt again into the 

 substance of the body when they are withdrawn. 



Five distinct types of structure are known in the Rhizo- 

 poda, and these constitute as many distinct orders, which are 

 known by the names of the Monera, Amoebea, Foraminifera, 

 Radiolaria, and Spongida. 



ORDER I. MONERA. This name has been proposed for a 

 small group of organisms which merely require to be men- 

 tioned. They are all microscopic in size, and inhabit the sea. 

 Their sarcode-body is entirely structureless and devoid of defi- 

 nite organs of any kind. They have the power, however, of 

 throwing out innumerable processes of the body-substance or 

 " pseudopodia," and these agree in their characters with those 

 which will be afterward described as characterizing the Fora- 

 minifera. They are, namely, very long and delicate filaments 

 of sarcode, which unite in various directions so as to form a 

 net-work, in which the particles of food are entangled. The 

 body is completely naked, and the Monera differ from the 



