PROTOZOA 



in a mass at the inner end of the gullet, become separated 

 from it as a food ball (Yig. 14), and sink into the soft pro- 

 toplasm of the body. The food balls 

 follow a circular course through the 

 endoplasm, keeping near the ectoplasm. 

 Reproduction. This, as in the ameba, 

 is by division, the constriction being in 

 the middle, and part of the nucleus going 

 to each half. Sometimes two individ- 

 uals come together with their 

 mouth-grooves touching and 

 exchange parts of their nuclei 

 (Fig. 1 6). They then separate 

 and each divides to form two 

 new individuals. 



We thus see that the para- 

 mecium, though of only one 

 cell, is a much more complex and advanced 

 animal than the ameba. The tiny paddles, 

 or cilia, the mouth-groove, etc., have their 

 special duties similar to the specialized organs 

 of the many-celled animals to be studied later. 



If time and circumstances j 



allow a prolonged study, sev- 

 eral additional facts may be 

 observed by the pupil, e.g. 

 Does the paramecium swim 

 with the same end always 

 foremost, and same side 

 uppermost ? Can it move 

 backwards ? Avoid obsta- 

 cles ? Change shape in a 

 narrow passage ? Does refuse FIG. 19. SHELL OF A RADIOLARIAN. 



FIG. 17. VORTI- 

 CELLA (or bell 

 animalcule), two 

 extended, one 

 withdrawn. 



FIG. 18. 

 Euglena. 



