GENERAL NOTES ON TUNIC AT A. 



435 



respiratory current as in the Ascidians, and the gill-slits may be few in 



N M 



DO 



En 



FIG. 213. "Nurse" oiDoliol/em miilleri. After Uljanin. 



I., inhalant, E., exhalant aperture; C., ciliated band round 

 pharynx (P) ; En., endostyle ; O., otocyst ; X., nerve-gang- 

 lion; H., heart ; (E., oesophageal opening ; D., stomach ; A., 

 anus ; Cl., cloaca ; DO., dorsal organ ; M., muscle bands. 



number, or, as in Salpa, may be represented by two large holes in the 

 walls of the pharynx. Further, the hermaphroditism is modified by the 



FIG. 214. Sexual individual of Dollolum miilleri. 

 After Uljanin. 



G., gonads ; B., gill-slits ; other letters as before. The unlettered 

 reference line points to the stomach. 



occurrence of very marked protogyny, and the ova are never numerous 

 in Salpa each sexual individual usually produces only one. 



