i88 



H^MATOCOCCUS (SPHAERELLA) 



The normal green colour of the individuals of H ' cematococcus 

 is often obscured by the accumulation of a bright red pigment 

 (haematochrome) which appears particularly at certain times, 

 when, with the withdrawal of the cilia and thickening of the 

 cell-membrane, the individuals round off to form characteristic 

 resting-stages (Fig. 98, B). If these occur in quantity they may 

 lend a deep red colour to the water or mud. This simple method 

 of entering upon a resting-stage is also encountered in a few 

 species of Chlamydomonas (e.g. in red snow), but is much rarer 

 there than in H cematococcus. Reproduction of the latter is 

 effected in almost the same manner as in Chlamydomonas, the 



sexual process 

 always being 

 isogamous. 



Chlamydo- 

 monas, Carteria, 

 and H cematococ- 

 cus are but re- 

 presentatives of 

 a whole class 

 of simple green 

 plants, all of 

 which swim 

 about like ani- 

 mals during the 

 greater part of 

 their life, 1 and 



m^st of which are inhabitants of fresh-water. In some 

 genera the unicellular individuals are combined in different 

 ways to form definite groups or colonies. Such is Eudorina 

 (Fig. 99), which is commonly to be found in small pieces of water 

 among the slimy growth covering submerged parts of higher 

 aquatics. The colony here consists of 16, or more commonly 32, 

 globular cells embedded at regular intervals in the peripheral 

 portion of a spherical or oval mass of mucilage. Each indi- 

 vidual cell is almost identical in structure with a Chlamydomonas- 

 plant, the two cilia projecting well beyond the mucilage-invest- 



1 In their mode of nutrition, however, they are altogether plant-like, 

 and there is no justification for placing them in the Animal Kingdom. 



FIG. 99. Eudorina elegans. A, Vegetative colony ; 

 the cilia are seen on three of the individuals. 

 B, A colony showing vegetative reproduction, 

 the daughter-colonies being in various stages of 

 development. 



