44 ZOOLOGY DIRECTIONS 



12. Nuclei. Division of labor is accompanied by a spe- 

 cialization of the nuclear material in the Ciliates. Instead of a 

 single nuclear mass there are two nuclei in each cell. The larger 

 of these, called the macronucleus, seems to have control of the or- 

 dinary bodily functions, Avhile the fnicronucleus is concerned 

 chiefly in the reproductive process. These nuclei are not observ- 

 able in the living animal. At the demonstration table examine 

 stained specimens. 



13. By use of the ocular micrometer measure the length 

 of the entire animal, the macronucleus, and micronucleus. Use 

 these measurements to insure correct proportions in drawing 

 asked for in next paragraph. 



14. Make a large drawing, 150 mm. long, of a living Para- 

 mecium, side view, locating and labeling various structures. 

 Show structure carefully in part of drawing 1 cm. back from the 

 anterior end of the body. In remainder of body show division 

 between ectoplasm and endoplasm by dotted line. Nuclei seen in 

 stained demonstrations should be shown in this drawing. Indi- 

 cate direction of protoplasmic currents by a series of arrows 

 showing course through the entire cell. 



15. Reproduction by simple transverse fission. If possible 

 watch and sketch the process in living specimens. Time for 

 process of fission ? How many mouths just before fission is 

 completed? How many contractile vacuoles? Are the two re- 

 sulting individuals alike? See stained demonstrations. 



16. Look for pairs of Paramecia undergoing conjunction. 

 See demonstrations. 



REFERENCES 



Calkins, G. N., 1926. The Biology of the Protozoa. Lea and 

 Febiger, Philadelphia, Penn. 



Maier, H. N., 1903. Ueber den feineren Ban der Wimperap- 

 parate for Infusorien. Arch, f . Protist. Bd. 2 :72-179. 



Minchin, E. A., 1912. An introduction to the study of the Pro- 

 tozoa. Arnold, London. 



Woodruff, L. L., 1922. Foundations of Biology. Macmillan, 

 N. Y. 



