VORTICELLA 63 



raised in the form of a dome or plate, forming the disk. 

 Between the peristome and the disk is a gutter-like depres- 

 sion leading into a deep pit, the vestibule. Is there anything 

 in Paramecium which corresponds to this vestibule? From 

 the vestibule the esophagus extends downward. Trace its 

 direction and determine its shape. In Vorticella where 

 are the cilia located and how are they arranged? 



In the body look for a transparent covering, the cuticle. 

 Is there ectoplasm and entoplasm as in Amoeba and Para- 

 mecium? Is the differentiation of these layers as marked 

 as in the other protozoa studied? Are food vacuoles present? 

 Are there contractile vacuoles ? How many? Where located? 

 The nucleus is an elongated horse shoe or "C" shaped mass 

 in the entoplasm. It may be more easily found if the animals 

 are stained with methyl green. A micronucleus is present, 

 but is so small as to be found only with great difficulty. 



II. Physiology. 



1. General Movements. Observe the manner in which the 

 stalk contracts. What changes take place in the body 

 during this contraction? May the body contract without 

 a contraction of the stalk? Note the rapidity of the move- 

 ments in the contraction and in the expansion. How does 

 the animal assume the expanded condition? Which is the 

 part to first assume the expanded condition? Note that 

 in some cases there is no stalk attached to the animals. How 

 do they behave when this is the case? Vorticella may 

 separate from its stalk and become free-swimming for a time. 

 During this period a second row of cilia develops about the 

 base of the bell, to aid in locomotion. (In some cases this 

 separation from the stalk is not normal, but is due to pressure 

 from the cover glass or to some other unusual condition; in 



