442 University of California Publications in Zoology [Vol.19 



were always active with that effective stroke which normally tends to 

 drive the animal forward. The membranelles on the right side of the 

 cut occasionally moved in coordination with the former or sometimes 

 did not move in the least but projected straight out from their bases. 

 Not infrequently, they were distinctly seen to beat with the effective 

 stroke in the opposite direction to that of the series on the left side of 

 the cut. Carmine granules or india ink which had been introduced 

 into the water clearly indicated these three changes in the behavior of 

 the adoral membranelles on the right side of the cut. It will be noted 

 that the membranelle fiber at the base of these membranelles on the 

 right side of the incision was continuous and in connection with the 

 motorium. These results of such experiments were very obvious and 

 remarkably uniform. 



Incision through the membranelle fiber at any point posterior to 

 the oral lip (fig. 6). — Differences between the rhythm and direction of 

 the effective stroke of the membranelles anterior to the incision and 

 of those posterior were apparently identical with those just described 

 above. However, the swimming movements following such incisions 

 were practically normal. Some animals (three especially were noted) 

 were less active after the incision and showed more tendency toward 

 circus movements ; otherwise, their swimming and creeping reactions 

 were comparatively normal. 



Incisions on the right or left side or at the posterior end did not 

 sever the cytostomal fiber or any of the anal cirri fibers. — Following 

 such incisions made in many animals at various angles through the 

 maeronucleus or not (figs. 10-12) I have never as yet observed any 

 noteworthy change in their normal swimming or creeping reactions or 

 in the perfect coordination between the series of membranelles and the 

 anal cirri. 



Incisions severing all the anal cirri fibers. — Incisions were made 

 (1) on the right side between the group of three and the group of 

 four frontal cirri (fig. 7) ; (2) on the right side between the group of 

 four frontal cirri and the two ventral cirri (fig. 8) ; and (3) on the 

 right side between the two ventral cirri and the five anal cirri (fig. 9). 



After severing the anal cirri fibers at any one of these three regions, 

 two significant changes were evident in creeping and three in swim- 

 ming movements: (1) there was distinctly less tendency to creep; the 

 animal when not swimming was more frequently found quiet on the 

 surface of the cover-slip, on the surface film of the hanging drop or 

 upon debris. But when creeping, the anal cirri were used with less 

 sureness and facility than normally. That much was commonly evident 



