454 



Table 2. 



59 

 5o 



49 



Tlie central column represents the 

 time, divided into half minutes. 

 Each minute is numbered. Each 

 of the lines on the sides represents 

 a lieart reversal. The second in 

 which it occurred is indicated hy 

 the number at the end of the line. 

 The distances between the lines 

 correspond to the length of the 

 reversal periods ; + denotes a 

 posterior and — an anterior di- 

 rection of the blood in the heart. 



heart reversed is added at the end of each liue. 

 A plus sign is inserted in those intervals in 

 which the blood flowed posteriorly, the op- 

 posite direction being indicated by the op- 

 posite sign. The table shows that there is a 

 tendency for the reversal of both hearts to 

 take place at nearly the same time, but this 

 tendency is about as strong when the hearts 

 are beating in the same as in opposite direc- 

 tions. Thus, near the top of the table, the 

 reversals take place nearly as was stated by 

 Pizon, but at the bottom exactly the oppo- 

 site occurs. During the whole time of the 

 obsei*vation the hearts were beating in the 

 same direction for S34 seconds, and in oppo- 

 site directions for 824 seconds. Accordingly, 

 even in this most favorable case, it is evident 

 that there is no tendency for the hearts of a 

 colony to beat in the same direction. 



Relation between Heart Beats and 

 Ampullar Pulsations. 



Piz ondescribes the reversal of the hearts 

 as being synchronous with the reversal of the 

 flow of blood in the ampullae, and seems to 

 think that the direction of the flow in the 

 latter depends upon pressure derived from 

 the hearts. Three series of observations to 

 determine the influence of the hearts upon 

 the ampullar contractions were made. In each 

 case a number of ampullae that contracted 

 synchronously were observed and the rever- 

 sals of the blood flowing in and out of them 

 compared with the heart reversals of the nea- 

 rest zoöid. In one case this zoöid was con- 

 nected with the ampullae observed by a com- 

 plex network of blood vessels having the most 

 various relations whith the rest of the colony, 

 so that probably the greater portion of the 

 blood supply was not derived from the zoöid 

 with which they were compared. In another 

 case the ampullae were in intimate vascular 



