UNICELLULAR ORGANISMS 



73 



CHILOMONAS 



This is an example of a still more minute organism found very 

 abundantly the world over in water among decaying leaves. 

 From Figure 26 it will be seen that its structure 

 is extremely simple. It has a slightly elongated 

 oval body, with a little depression at one end, 

 at the bottom of which food is taken into the 

 animal, the depression serving as a mouth. There 

 are no internal indications of organs, except a 

 small nucleus. At one end are two filaments 

 called flagella (Lat. flagellum = a whip), which 

 have the power of lashing to and fro. By means 

 of their lashing the Chilomonas is driven through 

 the water. Chilomonas multiples by simply dividing FIG. ' 26. 



into two, essentially in the CHILOMONAS 



A very mi- 



same manner as Amceba. nute, flagellate, 



unicellular ani- 

 mal, found in 

 PANDORINA stagnant water. 



Pandorina is an animal very similar 

 in its general structure to Chilomonas, 

 except that it is made up of a number 

 of cells grouped together, instead of 

 a single individual body; Fig. 28 A. 

 The method by which this group is 

 formed is simple. The animal starts 

 as a single cell, which divides, but 



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ANIMALS, RELATED TO after division the parts, instead of 

 CHILOMONAS separating at once, remain attached, 



A,Gymnodinium; B,Ceratium. i 11 / i 



and there arises a group of sixteen 



cells attached together. They secrete a little mass of jelly 

 around themselves and the flagella projecting through this 

 jelly enable the whole spherical mass to be rotated as a 

 unit. The individual members are somewhat independent of 

 one another, but are attached so as to form one single unit. 

 Such a group is called a colony. 



FlG. 27. TWO SINGLE-CELLED 



