112 University of California Publications. [zoology. 



heart without in any way injuring- it. These contractions do not 

 appear to have been ante-mortem phenomena like those observed 

 by Schultze. but rather an exaggeration of the similar contrac- 

 tions described by Loeb at the time of reversal, for at first they 

 alternated with the normal series of contractions, and were finally 

 entirely replaced by the normal series. 

 Pulsations from the center of the heart were observed: 



1. In 2 cases out of the 7 described above in which the heart 

 was isolated without injury. 



2. In two cases out of 63 in which one end of the heart had 

 been isolated from the remainder. 



3. In 8 out of 28 half hearts obtained by tying the heart 

 across its center. 



4. Occasionally in still smaller pieces. 



In sonic of these cases the contractions came steadily from 

 the center, while in others the direction was sometimes reversed. 



Reversals in pieces oftht heart subjected to no external influ- 

 ences, except the sea water in which they were immersed, were 

 noted : 



1. In 2 hearts from which only one end had been removed. 

 Series of pulsations from the center alternated with series from 

 the intact end. 



2. In 3 of the 28 half hearts: Series from the center alternat- 

 ing with series from the end. 



3. In 4 out of 82 still smaller pieces one cud of which was an 

 intact end of the heart. 



-t. In 3 out of 158 pieces which were not connected with an 

 end of the heart. In one of these, scries from the center alter- 

 nated with series from one of the cut ends, in the others the con- 

 tractions began at the cut ends. 



These observations on contractions from the center and the 

 reversal of small pieces of the heart show that the heart of Ciona 

 as obtained at San Pedro is of a more uniform character through- 

 out its whole extent than had been formerly supposed. The 

 tissues at the end are of such a character that ordinarily the con- 

 tractions start there. But the center resembles them so closely 

 that even in the intact heart contractions may originate in that 

 place. In fact, all parts of the heart are so remarkably similar 



