455 



Table 3. 



connection -with the zoöid, probably deriving most of their blood from it, 

 but were also connected with the rest of the colony by another vessel. In 

 the third case all vessels connecting the ampullae with other parts of 

 the colony were severed, thus realizing the conditions which would 

 most facilitate any possible influence of the heart beats upon the am- 

 pullar contractions. In all three cases the results were the same. The 

 ampullae pulsated in a rythm of their own which was independent of 

 and considerably shorter than the reversal periods of the zoöids. 

 Table 3 represents the coordination between ampullar contractions 

 and reversal period in the third case, when the ampullae were connec- 

 ted only with one zoöid. The vessels were so arranged that when the 

 heart propelled the blood in an anterior direction the tendency w^as 

 to force it into the ampullae, and vice versa. 

 Accordingly, in the column for the ampullae 

 the -4- sign stands for the systole of the am- 

 pullae which would tend to drive the blood 

 in the same direction as the -\- or posterior 

 contractions of the heart. Similarly the am- 

 pullar diastole is indicated by the — sign 

 and has the same effect on the blood as the 

 — or anterior contractions of the heart. A 

 glance at Table 3 suffices to show the entire 

 absence of coordination between the ampullar 

 pulsations and the heart reversals, even under 

 these most favorable circumstances. Inspec- 

 tion showed that there was a slight influence 

 of the heart beats upon the ampullar circu- 

 lation, the latter being less vigorous when 

 opposed by the heart. The opposing pressure 

 also seemed to help determine the exact 

 moment when the ampullar systole or diastole 

 commences, though it does not perceptibly 

 influence the flow of blood at other times. 



The contractions of the whole zoöid, however, were so vigorous that the 

 ampullae could not resist them ; and thus the blood was occasionally 

 forced back into the ampullae for an instant in the middle of a systole. 

 But as the contractions of the zoöids were usually only a few seconds 

 long the blood very soon flowed back in the original direction. In con- 

 clusion then it may be said that the ampullae evidently have an inde- 

 pendent power of contraction, and an independent rythm that is influ- 

 enced but little by the zoöids of the colony. 



The lines to the left of the tims 

 column represent the reversals of 

 the flow of hlood in the am- 

 pullae; those to the right the 

 reversals of the he art. + indi- 

 cates the ampullar systole and 

 — its diastole. For other expla- 

 nations see Table 2. 



