50 Viiiversitu of California Publicalions iii Zoology [Vol.20 



Locomotor Organelles: The surface of the anterior two-thirds 

 or more of the body is covered with cilia or flagella. Both terms are 

 not inappropriate here, since three distinct lengths of this hairlike 

 covering is found in this species, in three distinct zones or locations. 

 At the anterior end of the body is a zone of long, threadlike flagella 

 (fig. B, ant. fi.; pi. 5, fig. 1), that may have a length equal to one- 

 third that of the body. These arise from the narrow portion imme- 

 diately behind the operculum, directly from the centroblephai-oplast 

 or its immediate branches. Posterior to this group and extending 

 backward for slightly more than half the length of the body is a thick 

 covering of short, cilia-like hairs (fig. B, cil.; pi. 5, fig. 1) of uniform 

 length. These have a length of one-fourth to one-fifth or less of the 

 anterior flagella. In apparent texture and thickness they seem to be 

 similar to the longer flagella of both the anterior and posterior regions, 

 differing from them only in length. 



The third zone of long flagella is found between the distal limits 

 of the short cilia and the posterior end of the ectoplasmic differentia- 

 tion of the surface of the body (fig. B, post, fl-.; pi. 5, fig. 1). These 

 are considerablj^ longer than the flagella of the anterior zone, often 

 having a length equal to that of the entire body (fig. A). They extend 

 posteriorly, trailing after the body when in motion, and often inter- 

 secting (fig. A, 1) or twisting around in a loose spiral (figs. A, 2, 4). 



The anterior group of flagella seems to be the chief means of 

 locomotion. When the organism is at rest constant vibratory waves 

 pass through the entire coating of cilia and flagella, beginning at the 

 anterior end and passing posteriorly to the tip of the longest flagella, 

 but dying out in intensity distally. These vibrations continue in the 

 cilia and posterior flagella when the flagellate is in motion but the rate 

 of movement of the anterior flagella is greatly accelerated. They are 

 thrown out in longer and stronger vibrations, resulting in a rapid 

 movement forward of the body. 



Flagella intermediate in length between these three groiqjs are not 

 infrequent (pi. 5, fig. 3) near the margin of the areas. In T. agilis, 

 as figured by both Leidy (1881) and Porter (1897), the entire area 

 of short cilia is replaced by flagella intermediate in length between 

 the short anterior group and the longer posterior flagella. This results 

 in a thick coat of long flagella for nearly the entire body in that 

 species. 



Each flagellum or cilium in T. campanula arises from a minute 

 basal granule below the ridges of the surface of the body (pi. 12, 



