PROTOZOA 



15 



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 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 

 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withdrawn. 



