294 KANSAS UNIVERSITY SCIENCE BULLETIN. 



be mistaken for the mouth, but the mouth is just ventral to it 

 and convenient to the currents set up by the flagellum. 



The gullet is a long, narrow funnel running obliquely up- 

 wards and backwards until it nearly reaches the opposite side 

 of the body. Like other protozoa of this group, it is supported 

 by calcareous rods. These are plainly visible when picro- 

 sulphuric acid is first placed on the specimen, but very soon the 

 acid destroys them and the gullet shows only as a clear place 

 in the protoplasm. 



Two contractile vacuoles are present, and a very large nu- 

 cleus. The nucleus is especially interesting in these forms be- 

 cause the meganucleus is heterogeneous, the anterior half re- 

 maining almost clear when stained with picro carmine, the 

 posterior half staining densely. The micronucleus may lie 

 quite far to the posterior end of the meganucleus. The fact 

 that the two halves of the nucleus react differently to the 

 same stain suggests a segregation of functions. Since in di- 

 vision the meganucleus breaks transversely, the resulting ani- 

 mals are dimorphic as to meganuclear protoplasm. 



CLASSIFICATION. 



According to Lankester's classification the specimen de- 

 scribed above belongs to the sub-order Gymnostomata, that 

 division of the Holotrichs in which the mouth is closed in the 

 intervals between the acts of ingesting food. It belongs to the 

 family Dysterinae (Clap. & Lach.), which corresponds to Calk- 

 ins's sub-family Ervilinse: Cilia confined to ventral surface 

 or a portion of it; caudal end invariably possesses a movable 

 style arising from caudo-ventral surface. 



Of the various genera grouped under this family, or sub- 

 family, our specimen corresponds most closely to the last of the 

 following list : 



^gyria (Clap. & Lach.), 1858. 



Onychodactylus, Entz, 1884. 



Trochilia, Duj., 1841. 



Dysteria, Huxley, 1857. 



Dysteropsis, Roux, 1902. 



The only species of this genus, so far as I can learn, is the 

 small one found in the lakes of Geneva and called minuta by 

 Roux, because it measures only 28 micra long and 16 micra 

 wide. The animal described in this paper is marine; the av- 



