28 PROTOZOA [CH. 



networks are much coarser than in the case of the Thalamophora. 

 The fluid endoplasm is seen to have a regular flow alternately 

 backwards and forwards in these pseudopodia ; the movement of 

 the whole mass in any direction heing due to the predominance of 

 the forward flow over the backward, or vice versa. When stained 

 the protoplasm is seen to include thousands of very small nuclei. 

 The name Mycetozoa literally means Fungus animals (from Gr. /XVK^?, 

 a fungus, <3a, animals). They are also often called Myxomycetes 

 literally Slime-Fungi, both names having been suggested because 

 their special mode of reproduction leads some naturalists to con- 

 sider them to be plants. Their power of encystment is very marked, 

 for the slightest tendency to drought calls it into action, and then 

 a mass will break up into numerous cysts, which will remain perfectly 

 passive until wetted. Before reproduction, the same process occurs, 

 but the nuclei multiply by division and then fuse in pairs with one 

 another; the contents of the cyst then become aggregated round 

 these final nuclei as rounded germs called spores which acquire 

 walls of cellulose, a constant product of plant life. Such spores 

 are called chlamydospores. In one group of the Mycetozoa known 

 asEndosporeae a portion of the plasmodium swells up so as to 

 form a rounded mass on a stalk which is termed the sporangium 

 and which encysts itself. In another group lobe-like fingers grow out 

 from the plasmodium, from the apices of which spores are constricted 

 off one by one. These are called the Exosporeae. Some of the 

 protoplasm not used in the formation of spores forms long threads 

 of cellulose, called collectively a capillitium, which when wetted 

 expands and so expels the spores. The appearance of cellulose 

 was the only justification for regarding these animals as in any 

 way allied to plants, and it is known that cellulose is quite a 

 constant product in some groups of animals. The contents of the 

 spore escape as a germ propelling itself by a flagellum (B and C, 

 Fig. 7), the germ itself being termed a flagellula. This thread is 

 soon withdrawn and the germ takes on the form of a small Amoeba 

 and is then called an amoebula (D, E, and F, Fig. 7). Many of 

 these amoebulae coalesce to form the adult form, which is called the 

 plasmodium (G, Fig. 7), a name given to the result of the fusion 

 of a number of originally separate animals. 



The Sun animalcules, or Heliozoa (Gr. -9X109, the sun), which 

 inhabit, with few exceptions, fresh water, were formerly 



Heliozoa. . ^ ' / 



confounded with the Radiolana, but they are in 

 reality very different from these. They are spherical in shape and 



