36 MANUAL OF ZOOLOGY sect, i 



free pseudopodial movements which characterise the Rhizo- 

 poda, is precluded by the presence of a very thin skin or 

 cuticle which invests the body. There is a nucleus (nu) 

 near the centre of the body, and at the anterior end a con- 

 tractile vacuole (H, c. vac), leading into a large non-con- 

 tractile space or reservoir (r) which discharges into the 

 gullet. 



The greater part of the body is coloured green by the 

 characteristic vegetable pigment, chlorophyll, and contains 

 grains of paramylum {H, p), a carbohydrate allied to 

 starch. In contact with the reservoir is a bright red speck, 

 the stigma {pg), formed of a pigment allied to chlorophyll 

 and called ho&matochrome. It seems probable that the 

 stigma is a light-perceiving organ or rudimentary eye. 



Euglena is nourished like a typical green plant ; it de- 

 composes the carbon dioxide of the air dissolved in the 

 water, assimilating the carbon and setting free the oxygen. 

 Nitrogen and other elements it absorbs in the form of min- 

 eral salts in solution in the water. But it has also been 

 shown that the movements of the flagellum create a whirl- 

 pool 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 (liolozoic) with the characteristically vegetable (Jwlo- 

 phytic) mode of nutrition. 



Sometimes the active movements cease; the animal comes 

 to rest and surrounds itself with a cyst or cell-wall of cellulose 

 (the characteristic material of the cell-wall of plants), from 

 which, after a quiescent period, it emerges to resume active 

 life. It is during the resting condition that reproduction 

 takes place by the division of the body in a median plane 

 parallel to the long axis (G). Under certain circumstances 



