410 ZOOLOGY. 



may float on the surface of the water or adhere to the 

 sides or bottom of the receptacle. 



Sometimes cysts are formed in which the cell is sur- 

 rounded by a thicker and more resistant envelope of a 

 yellowish-brown colour. Division takes place also within 

 these cysts, but the details are not distinctly visible. In 

 other species division has been observed to occur in the 

 motile condition, and repeated division may occur in the 

 resting state so that a number of very small individuals 

 are formed and ultimately set free. 



PARAMYLUM BODIES 



STIGMA 



NUCLEUS 



Fig. 204 EUGLKNA 8PIROGYB.A, AFTER STEIN. 



8. Specific Characters. There are a number of species 

 resembling Euglena viridis in general characters but differ- 

 ing in minute details, and there is another group of species 

 in which the chloroplasts, instead of being elongated and 

 rod-like or stellate, are small separate discs like those of 

 plants. To this latter group belongs the ~E. spirogyra 

 shown in fig. 204. This group again can be divided into 

 two divisions : (1) those species in which each chloro- 

 plast contains a pyrenoid, (2) those in which it does not. 

 Where a pyrenoid is present in the chloroplast it forms a 

 layer of paramylum outside itself on each side, but paramylum 

 also occurs in the cytoplasm independently of the chloro- 

 plasts. Thus in E. spirogyra and other species there are 

 two large annular bodies of paramylum, one in front of 

 and the other behind the nucleus. In other species again, 

 as in E. deses, there are more than two paramylon bodies 

 in the cytoplasm unconnected with the chloroplasts. 



9. Mode of Nutrition. We have seen that there is iA> 

 evidence that Euglenae ingest solid particles of food and 

 digest them. In other words, the nutrition is not holozoic 



