238 EDNA MCXALLY. 



The nuclear complex is peculiar in that it is not differentiated 

 into micro- and macro-nuclei but is very similar to the nucleus 

 of Amoeba proteus. This statement does not agree with Cohn 

 (53), who says of N. elegans, "Nucleus elliptic, with nucleolus 

 lodged at one end." And Pritchard (61), with N. elegans in 

 mind, thinks the "nucleus is stoutly clavate, and terminated by 

 a small oblong nucleolus at its narrower extremity." The 

 nucleus does not occupy a fixed position but is moved around 

 by the streaming of the protoplasm. 



The mouth opens into a pharyngeal apparatus composed of 

 about twenty-five pharyngeal rods arranged in the form of a 

 truncated cone, with the base anteriorly directed. This pharyn- 

 geal apparatus is described by all of the above mentioned authors 

 for all species with the exception of Cohn (53), who states that 

 there is no such apparatus in N. elegans. About one third of the 

 way posterior to the base of this basket-like cone appears to be 

 a "band of refractive protoplasm," as described by Eherenberg 

 (oo), for N. elegans. Nothing was said of this ring in N. ornata. 

 However, I have been able to demonstrate this ring in prepared 

 material of both species. Eherenberg probably overlooked it in 

 living specimens of N. ornata because of its being obscured by the 

 food vacuoles. This mechanism seems to serve as a support to 

 the pharyngeal rods and also aids in drawing Oscillatoria filaments 

 through the pharynx into the body of the animal. 



Food vacuoles are numerous and vary in number and color 

 with the amount of food injested and the stage of digestion of 

 this food. A freshly fed Nassula contains so many food vacuoles 

 of such dark color that the other morphological details cannot 

 be made out with certainty. Just after injestion of food the 

 vacuoles are brown or dark green due to the color of the Oscilla- 

 toria, but as digestion proceeds they are changed to a shade of 

 purple, then pink and finally faint straw color. All these stages 

 may be encountered at one time in the same individual. 



The contractile vacuole, of w r hich there is but one, is peculiar. 

 It is stationary and is the point toward which the streaming of 

 the protoplasm is directed. As metabolism ensues minute 

 vacuoles of clear fluid are formed throughout the protoplasm. 

 \Yith the streaming of the protoplasm these vacuoles are brought 



