174 



THE PROTOZOA 



quite broad or very narrow. As a rule, the thicker the pseudopod the 

 more rapid the movement. Some rhizopods have hard shell-like 

 coverings which are secreted in or on the ectosarc. These skeletons 

 have openings through which the pseudopods project. The pseudopo- 

 dia may be made up only of ectoplasm or both ectoplasm and endoplasm 

 may take part. Amoeboid movement always starts in the ectoplasm. In 



FIG. 56. Various protozoa. i, Entamoeba coli; 2, Entamoeba histolytica; 

 3, Leydenia gemmipara; 4, Trichomonas vaginalis; 5, Trichomonas intestinalis; 

 6, Lamblia intestinalis; 7, flagellated Leishmania donovani; 8, Leishmania donovani 

 in phagocyte; 9, Eimeria stiedae; 10, Isospora bigemina; n, Trypanosoma gam- 

 biense; 12, Balantidium coli. 



addition to the nucleus, which the so-called chromatin staining methods 

 bring out as reddish areas, we frequently observe smaller aggregations 

 of chromatin staining material in the cytoplasm. This extranuclear 

 chromatin is supposed to play a part in the more intricate divisions 

 which such protozoa undergo. Food vacuoles and contractile vacuoles 

 are present in many rhizopods. 



