254 EUGLENA CHAP. 



Near the centre of the body or somewhat towards the 

 posterior end is a nucleus (e, nu) with a well-marked 

 nucleolus, and at the anterior end is a clear space (c. vac), 

 looking very like a contractile vacuole. It has been shown, 

 however, that this space is in reality a non-contractile cavity 

 or reservoir (h, r) into which the true contractile vacuole 

 (c. vac) opens, and which itself discharges into the gullet. 



In close relation with the reservoir is found a little bright 

 red speck {pg), called 'Cos. pigment spot or stigma. It con- 

 sists of hsematochrome (p. 243), and is curiously like an 

 eye in appearance, so much so that it is often known as the 

 eye-spot. Recent experiments seem to show that it is 

 specially sensitive to light, and is therefore a true eye in the 

 sense of a light-perceiving organ, although having no actual 

 visual function. 



As in Heematococcus a resting condition alternates with 

 the motile phase : the organism loses its flagellum and 

 surrounds itself with a cyst of cellulose (g, cy), from 

 which, aftSr a period of rest, it emerges to resume active 

 life. 



Reproduction takes place by simple binary fission of the 

 resting form, the plane of division being always longitudinal 

 (g). Sometimes each product of division or daughter-cell 

 divides again : finally the two, or four, or sometimes even 

 eight daughter-cells emerge from the cyst as active Euglense. 

 A process of multiple fission has also been described, 

 numerous, simple, minute, active bodies or spores being pro- 

 duced, which gradually assume the ordinary form and size. 



We have seen that typical animal-cells, such as those of 

 the frog (Part I, Chap. VII) are not provided with a 

 cellulose cell-wall and do not 'contain chlorophyll. It is 



