PEROPHORA ANNECTENS. 73 



counted in five individuals, the maximum in one direction 

 without a reversal was 208 in 2 min. and 9 sec, while the 

 minimum was 25 in i min. and 53 sec. 



In another individual examined, the examination besfin- 

 ning without counting, the contractions were found to 

 continue in the same direction for so Ions' a time that I 

 began to wonder if this individual formed an exception 

 to the rule governing the heart movements in Tunicates. 

 With this I began to count, and 302 strokes in the same 

 direction were performed in 7 min. before the reversal 

 took place. As I am quite certain that at least an equal 

 number of strokes were performed before the counting 

 began, and an equal time had elapsed, it would thus fol- 

 low that the strokes in the same direction without reversal 

 continued 14 minutes and were abovit 600 in number. 

 Of course, I have no means of knowing how long it ma}- 

 have been running in the same direction before my exam- 

 ination beiran. 



From my observations, it seems quite certain that the 

 total number of strokes in one direction is considerably 

 greater than those in the reverse direction. 



Thus, in one individual, of the 2,392 strokes counted, 

 1,485 passed from the ventral toward the dorsal side of 

 the animal, and 807 in the opposite direction; and in 

 every instance of reversal but three, the greater number 

 was in this direction. Similar results were obtained b}^ 

 observations upon several other individuals. Whether 

 the greater number of strokes is in the same direction for 

 all individuals, I am not certain. 



As one watches attentively the movements of the heart, 

 the impression is received that toward the close of a 

 period of contraction in a given direction, the fluid has 

 become condensed in the arterial vessels. A tendency 

 to regurgitation is frequently noticed at such times, indi- 



