72 CALIFORNIA ACADEMY OF SCIENCES. 



and this is one of the facts that leads me to think it 

 possible that another species niay be recognized on further 

 study. Certain it is, however, that the point cannot be 

 full}' determined until representatives not only of numer- 

 ous localities, but also of numerous ages of the colonies 

 and individuals, and of different seasons of the year, 

 have been carefully studied. 



Kowalevsky has stated ('74, p. iS), and his state- 

 ment has been contirmed by other observers, that in P. 

 Listcri the male genital products are matured before the 

 female; so that the hermaphroditism is protandric. 

 Whether this is true or not for this species is uncertain; 

 but the facts so far observed do not seem to indicate it. 

 In man}^ cases, as e. g. the one represented in fig. 19, pi. 

 ii, in which both sperm and ova are well developed, I see 

 no grounds for considering either as more nearly mature 

 than the other. In some individuals the ovary is consid- 

 erably more voluminous than the testis, while in others 

 again the reverse is true. I have never seen either sperm 

 or ova in the process of being discharged. 



7. CIRCULATORY SYSTEM AND BLOOD. 



The observations which I have made on this system 

 that seem to add anything to what is already known from 

 the study of other Tunicates, relate to the movements of 

 the heart and the character of the blood cells. x\s is the 

 case with other species of Perophora, so also in this one, 

 the great transparency of the living animal makes it very 

 favorable for studying the movements of the heart and 

 blood streams. I find that there may be great variations 

 in the number of beats in a given direction before the 

 reversal takes place to the opposite direction. Thus by 

 some observations made at Santa Catalina Island, during 

 the past summer, it was found that in about 4,000 strokes 



