FARAMCECIUIVI. 



Paramoecium, Stentor and other ciliated infusoria are usually abundant in 

 stagnant water. Opalina is often found in the rectum of the frog and newt. 

 . Examine a drop of water containing Paramoecia with a low power and observe 

 that they swim rapidly by means of their cilia, and that as they glide along they 

 usually rotate on their longitudinal axis so as to show distinctly at intervals the 

 mouth and pharynx on the ventral aspect. 



A. Arrange a few fibres of fine cotton-wool over the drop, apply a covering glass, 

 and examine with a higher power — 



1. The Ectosarc. 



Note (a) The thin cuticular layer perforated for the cilia. 



(6) That the cilia form an almost uniform layer except in the region of 

 the mouth where they are somewhat irregular and longer. 



(c) The striated layer, the lines running nearly longitudinally. 



(d) The two dorsally placed contractile vacuoles, from which several canals 



radiate — observe the rhythmical contractions of the vacuoles. 



(e) The trichocysts ; if not visible, they should be afterwards looked for, 



when acetic acid or some staining solution has been added. 



2. The Endosarc. 



Note (a) The granules moving in a definite direction. 



(6) The nucleus with a nucleolus at its side — may not be visible until 



acetic acid is added, 

 (c) The food entering the endosarc from the pharynx and following the same 



course as the granules, the food particles lying at first in food vacuoles, 



but at a later stage in contact with the protoplasm. 

 ((Z) That the undigested portions of food escape by an anal aperture which 



usually appears some distance from the mouth. 



B. Some of the Paramoecia may be fed with carmine, to show better the course of 



the circulation of the food particles, while others should be treated with acetic 

 acid or stained with majenta, to show the nucleus, nucleolus, and trichocysts. 



C. Examine with the low power and note if any of the Paramoecia are in contact 



with each other (conjugating) or in process of division by transverse fission. 



D. Make a diagram of Paramoecium, showing all the structures referred to, and 



draw any other Infusoria that may be present in the preparation. 



