76 CALIFORNIA ACADEMY OF SCIENCES. 



Thus at the close of his " Considerations Generales " 

 on the circulatoiy system of the Cynthiadie, he says, p. 

 93: " Enfin, cette structure speciale de I'appareil circula- 

 toire a determine, conjointement peut-etre avec la position 

 interne de I'organe de la respiration, le changement alter- 

 natif du sens des courants circulatoires, afin que le sang 

 arteriel puisse parvenir a tour de role dans tous les organes 

 (vo}^ memoire, No. 40, p. 141 a 151)."' Unfortunately 

 I have been unable to consult his paper here referred to. 

 The peculiar twisting of the heart during systole, such 

 as has been shown b}- Girard ('72) and Delia Valle ('81), 

 is represented in figure 11, pi. i. It is worthy of men- 

 tion that the twist is in the same direction which ever 

 direction the wave of contraction may be passing. 



THE BLOOD. 



As is apparently the rule among Tunicates, so likewise 

 in this species, the cells of the blood present a great 

 variety of size, form, and behavior towards reagents. 

 It is exceeding difficult to decide which of these are the 

 most typical and constant, or what is the relation between 

 the different varieties. After considerable study it seems 

 to me that four varieties may be recognized. 



One of these is represented by figures 35, 35^/, 35/-' 

 and 35c; a second by 36 and 36«; a third by 37, and a 

 fourth by 38, pi. iii. I describe the variety shown in 36 and 

 36^? first, because these differ less from the typical cell 

 than do any of the others — they are the least differen- 

 tiated. The form is usually nearly spherical; the nu- 

 cleus is large and round, contains a well defined nucle- 

 olus and a ver}- distinct nuclear membrane. The cell 

 protoplasm, rather small in quantity in proportion to the 

 size of the nucleus, is generally more deeply stained than 

 the bodv of the nucleus. The onl}- cases of cell division 

 amono- the blood cells have been found in cells of this 



