348 University of California Publications. [Zoology 



which takes place when the animal begins to swim. The basal 

 bodies of the cilia are located in the ectoplasm and at a point 

 below and to one side of the level of the myoneme. Maier ( :03) 

 has described in Spirostomum two kinds of cilia, those which 

 taper to a point and those that are hair-like having the same 

 dimensions thronghout. The cilia of the surface of the body of 

 Condylostoma fall under the latter class, being very long slender 

 filaments. They vary but little in length, those on the posterior 

 end being the longest. At this point they are arranged as a small 

 tuft and exhibit but little motion. As the animal glides over a 

 surface that is covered with minute debris, a great deal of it 

 catches in this tuft of posterior cilia. Maupas ('83) has called 

 attention to the difference between the distri])ution of the dorsal 

 and ventral cilia, those on the ventral surface being the longest 

 and fewest in number. As far as my evidence goes the dorsal 

 and ventral cilia are not differentiated either in structure or 

 number. 



Memhrancllae. — Such a complete account of the membra- 

 nellae has been given by Maier ( :03) that I shall only attempt 

 to give some of the characters as they appear in Condylostoma. 

 The membranellae have the appearance of large cilia as they 

 are rapidly beating. When the animals are compressed and 

 slowed down by the gelatin method, the ciliary appearance is lost 

 and they resemble fan-like organs. They are found along the 

 anterior edge of the buccal groove and down the left lip of the 

 peristome, down into the gullet around Avhich they wind spirally. 

 Those of the anterior edge are the largest, the size gradually 

 diminishing toward the posterior end. The position of those on 

 the left lip is such that the stroke is entirely within the gullet. 

 Those of the anterior edge beat in such a fashion that particles 

 are impelled to the left side. Each of these fan-like organs is 

 made up of a double row of fibers, each ending in a basal body 

 (PI. 34, fig. 6). The double row is only seen when the organ is 

 viewed from the side. The basal bodies lie embedded in the 

 ectoplasm and form a row at right angles to the direction of the 

 stroke of the organ. Around the bases of these bodies the ecto- 

 plasm thickens and forms a more or less well defined plate ex- 

 tending down into the endoplasm. This plate is called "Basal- 



