FLAGELLATED PROTOZOA 



53 



truncated plane and are then continued into the protoplasm as 

 far as the nucleus. The latter has a different structure from the 

 nucleus of Amoeba proteus and consists of a relatively large 

 granule (division center) surrounded by minute granules of 

 chromatin and without apparent nuclear membrane. Between 

 the nucleus and the truncated end of the cell is a somewhat 

 cone-shaped mass of denser protoplasm which is probably the 

 main seat of food assimilation. The remaining protoplasm has 



FIG. 21. Flagellated protozoa, Chilomonas and Euglena. The flagella of 

 Chilomonas have not re-appeared in the reproduction. Photographs from 

 preparations. 



a distinct alveolar structure, the alveoli about the periphery 

 being much more regular and compact than those within, the 

 whole giving a very excellent demonstration of the finer struc- 

 ture of protozoan protoplasm. A contractile vacuole, finally, 

 can be seen at one side of the truncated end. 



Chilomonas differs from Amoeba structurally in having a 

 definite and constant body form due to the presence of a firm cell 

 membrane easily seen in stained specimens. It also differs 

 from Amoeba proteus and from the majority of animals physio- 

 logically in that no solid food is taken in to be digested as in a 

 gastric vacuole of Amoeba. Nevertheless it could not live 

 without proteid food in some form, and the fact that it does live 

 and multiply to enormous numbers shows that it obtains suit- 



