436 University of California Publications in Zoology [Vol. 19 



generally results within an hour after the transection, but in three 

 cases this ceaseless activity continued for more than four hours. Any 

 indications of regeneration have not been observed. 



The posterior piece is much less active. It usually swims straight 

 ahead and occasionally in circuits to the right (cf. swimming move- 

 ments 1 and 3, p. 428) and very frequently revolves, then with obvious 

 difficulty, on the long axis. It remains most of the time inactive, 

 seldom creeps and always very slowly and feebly, and responds more 

 or less readily to jarring or to stimuli effected by the needle-point. In 

 the latter case its anterior end is very little if any more sensitive than 

 other parts of the body. A distinct avoiding reaction (cf. swimming 

 movement 6, and creeping movement 2, p. 428) has at no time been 

 observed. Use of the frontal and marginal cirri is conspicuously more 

 normal than is its use of the anal cirri, especially when attempting to 

 creep, as on the under surface of the inverted cover-slip. 



Experiment 106 (fig. 2). — Anterior piece swims very rapidly in right circus 

 movement with the three frontal cirri as a "moving center." Occasionally it 

 whirls and tumbles deviously about; it may then swim straight ahead revolving 

 two or three turns on its long axis, but very soon returns to circus movements. 

 It very seldom reverses the effective stroke of membraneles, even when needle 

 is thrust in its way. Frontal cirri beat continually as also do the membranelles. 



Posterior part mostly at rest with occasional movements of frontal and 

 marginal cirri less often of the anal cirri, except when another E. patella runs 

 into it; then it dashes for a short distance usually straight ahead. It then 

 bumps into piece of debris which it pushes straight ahead but does not go far. 

 Jarring starts its movements, which soon cease. Anal cirri are commonly 

 moved upon any lashing of the other cirri which is sufficient to move the body. 

 It would appear that they initiate such movement, which is then taken up by 

 the anal cirri. When stimulated with a needle point, its anterior end is little 

 if any more sensitive than are the sides or posterior end. 



Transection just posterior to the "group of four" frontal cirri 

 (fig. 3). — Anterior part swims in circus movements, although some- 

 what less completely than does the anterior piece above described. It 

 resorts more frequently to rotation on the long axis and to the reversal 

 of the organelles to drive the part backwards, although here, too, the 

 "rotation" movement is more common than the reversal reaction. The 

 part never creeps but swims rapidly and continuously for hours after 

 the operation. It does not turn sharply to the right (cf. swimming 

 movement 5, p. 429) and very seldom shows the avoiding reaction upon 

 being stimulated by the needle. After several hours the part may come 

 to rest on debris, on the surface film of the water or on the cover- 

 glass. It is then generally very sensitive to slight jarring or other 

 mechanical stimuli, whereupon its rapid swimming may be resumed 



