70 



ZOOLOGY 



SECT. 



and longitudinal lines in the outer layer of the protoplasm are due 

 to the presence ot elastic fibrils. There is a nucleus (nc, nu.) near the 

 centre of the body, and at the anterior end a contractile vacuole 

 (A y c.v.), or more than one, leading into a large non-contractile 

 space or reservoir (r.) which discharges into the gullet. 



The greater part of the body is coloured green by the charac- 

 teristic vegetable 

 pigment, chloro- 

 phyll, and contains 

 rod-shaped grains of 

 paramylum (A, p.), 

 a carbohydrate 

 allied to starch. In 

 contact with the 

 reservoir is a bright 

 red speck, the 

 stigma (st.), formed 

 of a pigment allied 

 to chlorophyll and 

 called hcemato- 

 chrome. It seems 

 probable that the 

 stigma is a light- 

 perceiving organ or 

 rudimentary eye. 



Euglena is nour- 

 ished like a typical 

 green - plant : it 

 decomposes the 

 carbonlf d i'o x i d e 

 dissolved in the 

 fQ water, assimilating 



the carbon and 

 evolving the oxy- 

 gen. Nitrogen and 

 other elements it 

 absorbs in the form 

 of mineral salts in 

 solution in the 

 water. But it has 

 also been shown 

 that the movements of the flagellum create a whirlpool by which 

 minute fragments are propelled down the gullet and into the soft 

 internal protoplasm. There seems to be no doubt that in this way 

 minute organisms are taken in as food. Euglena thus combines the 

 characteristically animal (holozoic) with the characteristically 

 vegetable (holophytic) mode of nutrition. But, in all probability, 



nu 



FiG. 52. Euglena viridis. A, view of entire organism, 

 showing details of structure (x about 1000); B, anterior 

 end, to show origin of flagellum, etc. ( x about 3000) ; 

 C F, four views of the living organism, showing the 

 changes of form produced by the characteristic euglenoid 

 movements ; G, resting form after binary fission, showing 

 cyst or cell-wall, nuclei, and reservoirs of the daughter- 

 cells ; ch chromatophores ; c.v. contractile vacuole ; cy. cyst 

 or cell-wall; fl,. flagellum ;fl'. thickening on flagellum ; fl". 

 bifurcated base of flagellum; gul. gullet; nc., nu.. nucleus ; 

 ncl. "nucleolus"; p. paramylum bodies; r. reservoir ; st. 

 eye-spot or stigma. (From Parker's Practical Zoology: 

 A, from Doflein ; B, from Dofleln. after Wager ; CG, after 

 Saville Kent.) 



