PROTOZOA 



pj 



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

 from it as a food ball (fig. 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. 16). 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 mucJi more complex and advanced 



animal than tJie 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 

 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 withdrawn.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. 



