430 Universi/u of Citliforniii I'ltlilirulions in Zoology [VOL. 19 



strongly stimulated mechanically, e.g.. by stirring the water violently. 

 This movement is often observed upon transferring an animal to the 

 hanging drop by means of a capillary pipette. The anal and marginal 

 cirri may aid in this movement but they are not essential. (Experi- 

 mental evidence will be given for this and following positive state- 

 ments.) 



(2) Spiral movement is the one most frequently observed. For 

 this movement, the marginal cirri are not essential, the anal cirri are 

 useful and the frontal cirri very valuable. "Without the adoral mem- 

 branelles the movement normally is quite impossible. 



(3) Circus movement to the right is frequently seen after the 

 animal has been confined in a narrow hanging drop which may be 

 either comparatively deep or shallow. The anal and marginal cirri 

 may aid in this movement but they are quite unessential. The frontal 

 cirri, particularly the ' ' group of three ' ' are useful here but the move- 

 ment is performed chiefly by means of the adoral membranelles. 



(4) Circus movement to the left is so infrequent that the means for 

 its accomplishment have not been studied. It has been observed only 

 when the animal was confined in a hanging drop. 



(5) The sharp turn to the right is performed chiefly by means of the 

 adoral membranelles and anal cirri. The marginal cirri are here useful 

 but not essential. The movement is very common. Usually the spiral 

 movement does not proceed far without this sharp turn intervening to 

 divert the animal's course. 



(6) The backward movement is effected chiefly also by the anal 

 cirri and always concomitantly with the reversal of the membranelles. 

 It is wholly an avoiding reaction and is distinctly comparable with the 

 creeping movement 2. Indeed, it may be regarded as merely the 

 augmentation of that movement 2, as shown by disturbing the creeping 

 animal sufficiently with the needle-point or by applying some chemical, 

 such as methylene blue. The animal may thereupon dash backwards a 

 distance several times its length, even repeating the movement again 

 and again. In this respect E. patella strongly reminds one of its 

 relative, Uronychia, whose avoiding reaction brings into play the large 

 posterior cirri which are seldom if ever otherwise used (Calkins, 1911, 

 p. 98). 



