41 



COPROMONA S 



1 



Copromonas (or Scytomonas, Fig. 2) is a flagellate which lives 

 in the moisture of dung. It is related to Englena but colourless, 

 as Polytoma is a colourless Chlamydomonas. It nourishes itself, 

 however, not as Polytoma does by absorbing through its surface 

 the products of decomposition amid which it lives, but by 

 swallowing through its gullet the bacteria which live in the same 

 solution. Its syngamy is performed solely by fully-grown ordinary 

 individuals. Usually the syngamy takes place when the dung is 

 becoming uninhabitable for the Copromonas, and the zygote 

 becomes encysted. From this condition it only emerges in fresh 

 dung, to reach which it must be swallowed in contaminated food 

 by a frog, and passed intact with the faeces. 



PERANEMA 



Peranema, common in stagnant water, is another colourless 

 relation of Etiglena. It is larger than Copromonas, pear-shaped 

 at rest but very active in changing its shape, has one flagellum, 

 rooted in a reservoir which opens in front of the gullet, and feeds 

 by swallowing smaller organisms into the gullet, the wall of 

 which is strengthened by stiff rods. Probably Peranema is also 

 saprophytic (see below). 



MODES OF NUTRITION 



The organisms which we have been discussing in this chapter 

 exhibit all the three types of nutrition practised by animals and 

 plants. In Chlamydomonas simple inorganic substances are 

 absorbed through the surface, and from them complex substances 

 are manufactured by means of the energy of the sun's rays. 

 Such organisms are said to be holophytic. In Copromonas and 

 Peranema complex organic substances are taken in through a 

 miouth, after the manner of animals. Such organisms are said 

 to be holozoic. In Polytoma, organic substances are absorbed in 

 solution through the surface of the body. Such organisms are 

 said to be saprophytic if they are plants, or saprozoic if they are 

 animals. The substances which form the food of various sapro- 

 phytic organisms differ a great deal. In Polytoma they are 



