does it behave when in contact with a solid body? Place a small 

 drop of salt solution colored with Chinese ink on a slide and note 

 whether the animals are sensitive to this substance. In similar man- 

 ner test them with i-io per cent and 1-2 per cent acetic acid, and also 

 with a bubble of carbon dioxide. Place animals on a slide heated at 

 one end and cooled at the other. What results ? In a similar man- 

 ner test them with the electric current and record your results. 

 Also test their sensitivity to light and gravity. 



II. VORTICELLA SP. 



(A Ciliate Protozoon). 



A. MORPHOLOGY. 



Examine filaments of algae, etc., for bell-shaped organisms borne 

 on a stalk. If a single individual is borne on a contractile stalk it 

 is some species of Yorticella ; if many individuals form a colony on 

 a common branched stalk it is some species of Carchesium or Zooth- 

 amnium (in Zoothamnium the stalk contains a common muscle 

 fibre which branches with the stalk) ; if the stalk is branched but 

 not contractile it is some form of Epistylis. Which genus are you 

 examining ? 



Study under high power and note : 



1. THE STALK, i. Shape; length compared with width. Shape, 

 when contracted and expanded. If branched, is there any regular 

 arrangement of the branches? 



2. Structure. Is there any distinction in the stalk between ecto- 

 plasm and endoplasm? The central axial filament or contractile 

 fibre is easily seen. Does it run in the exact center of the stalk? 

 Does it join the ectoplasm or the endoplasm at its upper end? 

 With your highest power study the structure of the axial filament. 



II. THE BODY. i. Shape, when seen from above ; from the side. 

 What is its shape when contracted ? When expanded ? In a fully 

 expanded individual observe: (a) The peristome or rounded edge 

 of the bell. Does it extend completely around the disk? (b) The disk, 

 a lid-like structure within the peristome raised on one side, (c) Be- 

 tween the peristome and the disk a ciliated depression leading down 

 under the raised portion of the disk into a deep pit, the vestibule. 

 Is there anything corresponding to this in Paramecium? 



2. Structure. Observe the following: (a) A transparent layer 

 covering the body, the cuticle. ( b ) Within the cuticle a clear 

 cortical layer, the ectoplasm. W r here is it thickest? (c) A central 



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