84 



PROTOZOA 



the tip by means of which the suctorian captures other protozoans and 

 passes them back to the mouth to be taken into the body. 



112. General Facts. — Protozoa vary in size from minute blood para- 

 sites which are barely visible to the highest powers of the microscope to a 

 gregarine, Porospora, which lives in the alimentary canal of the lobster 

 and which may be 17 mm., or % inch, in length. Most of them are not 



Nucleus 



B 



Nucleus 



Nucleus 



Fig. 33. — Some forms of Infusoria. A, a species of Podophyra. (After Biitschli, 

 " Klassen und Ordnungen das Tierreichs.") To illustrate the Suctoria. Highly magnified. 

 B, Opalina ranarum Purkinje. {From Kent, "A Manual of the Infusoria,'" after Zeller.) 

 An infusorian parasite of frogs. X 80. C, a species of Vorticella. (Modified from 

 Hegner, " College Zoology," after Shipley and Macbride.) Showing a portion of the attach- 

 ment stalk coiled. Highly magnified. D, Steritor polymorphus Mliller. {From Kent.) 



X 60. Attached individual. E, Balantidium coli Malmsten. {From Thomson and 

 Robertson, "Protozoology") X 400. F, Styloiiychia mytilus Ehrenberg. {From Kent.) 



X 100. (C by the courtesy of The Macmillan Company; E by that of William Wood & 

 Company.) 



visible to the unaided eye. The shapes of Protozoa are also exceedingly 

 varied. 



The cytoplasm of protozoans usually appears alveolar and is usually 

 divided into ectoplasm and endoplasm. Sometimes the nucleus is scat- 

 tered throughout the cell in small portions known as chromidia, when it is 

 called a distributed nucleus. We have already noted that in certain 

 cases there are two kinds of nuclei, the macronucleus and the micronu- 



