LIFE CYCLE OF NASSULA ORNATA AND NASSULA 

 ELEGANS: ARE THESE SPECIES VALID? 



EDNA McNALLY. 



I. DESCRIPTION. 



Nassula is a ciliated protozoan living in fresh water where 

 there is an abundance of Oscillatoria and not too much sunlight. 



Laboratory cultures of Nassula for these experiments were 

 maintained by placing them in ordinary square watch glasses 

 with spring water and fresh Oscillatoria, and these in turn, placed 

 in large covered glass vessels containing a small quantity of water. 

 The cultures were kept in subdued light as direct sunlight was 

 found to be fatal. All work on Nassula was done with pure 

 lines started from one individual and maintained for nearly a year. 



The genus Nassula was first described by Eherenberg about 

 1830. His description includes the species Nassula ornata and 

 Nassula elegans, the main difference between the two being color, 

 shape, and size. N. ornata he describes as being ovate or 

 cylindrical, dark green or violet in color and about 200-240 micra 

 in length. N. elegans, he gives as varying in color from red to 

 transparent, elongated, and about 160 micra in length (Eyferth, 

 1900). 



However there is great confusion in the classification of Nas- 

 sula. Pritchard (61), describes N. ornata and N. viridis as the 

 same species while Eyferth (oo), describes N. ornata and N. aurea 

 as the same. The species N. elegans as described by Pritchard is 

 exactly opposite to the description given by Cohn (53), for the 

 same species. 



Not only the species are confused, but also the genus, as is 

 shown by the following: "Stein hints it as probable that this 

 species (N. aurea) and N. viridis, Chilodon aureas and Ch. ornatus 

 are merely different stages of the same animal" (Pritchard, 61). 



The entire body of Nassula is covered with cilia appearing in 

 rows, approximately longitudinally disposed, over its surface. 



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