ii EUGLENA 251 



pairs to form zy gates (pp. 197, 237), each of which 

 becomes surrounded with a cell- wall, and after a time 

 again undergoes multiplication 



We will now examine, another small organism which 

 is often found in puddles and pools, frequently in. such 

 vast numbers as to give the water a green colour. This 

 organism is known as Euglena viridis. 



Euglena is also microscopic, its length varying from 

 J T mm. to J mm. The body is spindle-shaped, wide in 

 the middle and narrow at both ends (Fig. 69, A, C F) : 

 one extremity is blunter than the other, and from it 

 proceeds a single long flagellum (fl) by the action of 

 which the organism swims with great rapidity, the 

 flagellum forming a loop which travels along it. 

 Besides its rapid swimming movements, Euglena 

 frequently performs slow movements of contraction and 

 expansion, something like those of a short worm, the 

 body becoming broadened out first at the anterior end, 

 then in the middle, then at the posterior end, twisting 

 to the right and left, and so on (C F). These move- 

 ments are so characteristic of the genus that the name 

 euglenoid is applied to them. 



The organism consists of protoplasm covered with a 

 very delicate membrane or cuticle which is often finely 

 striated, and is to be looked upon as a superficial 

 hardening of the protoplasm. The colour is due to the 

 presence of chlorophyll, which tinges all the central part, 

 the two ends being colourless. It is difficult to make 

 out that the chlorophyll is lodged in a number of distinct 

 chromatophores (ch). 



In Sphaerella we saw that chlorophyll was associated 

 with starch (p. 243). In Euglena there are, near the 

 middle of the body, a number of grains of paramylum 

 (A, p) t a carbohydrate of the same composition as 



