XIII 



PHYLUM CHORDATA 



27 



muscular bands, which have the effect of driving the water back- 

 wards out of the branchial sac. 



c.c 



p.p 



end. 



FIG. 7:37. Salpa. Lateral view of a section which is sagittal (longitudinal, vertical and 

 median) in the oral two-thirds, and oblique in the atrial third, at. atrial cavity : 

 br. branchia ; c. c. ciliated crests on the edge of the branchia ; c. /. ciliated funnel ; rf. /. dorsal 

 lip ; end. endostyle ; ey. eye ; gl. digestive gland ; gn. ganglion ; ht. heart ; int. intestine ; 

 /</. languet ; mo. mouth ; ce. oesophagus ; m. ap. oesophageal aperture ; ph. pharynx ; pp. 

 peripharyngeal band ; st. (right) stolon ; st. (left) stomach ; c. /. ventral lip. (After Delage 

 and HeYouard.) 



Salpa (Figs. 736-737) is nearly allied to Doliolum in its 

 external features and internal structure. It has a fusiform body, 

 usually somewhat compressed laterally, and with the oral and 

 atrial apertures nearly 

 terminal ; but the mus- 

 cular bands do not form 

 complete hoops. The 

 pharyngeal and atrial 

 cavities take up the 

 greater part of the space 

 in the interior of the 

 body, where they form 

 an almost continuous 

 cavity, being separated 

 from one another only 

 by an obliquely running 

 vascular band, which re- 

 presents the dorsal lamina 

 of the fixed Ascidians 

 and is frequently termed 

 the branchia. 



Octacnemus , sometimes 

 regarded as allied to 

 Salpa, appears to be 



,, i i , i FIG. 738. Colony ui Pyrosoma. A, side view; />'. end 



fixed, IS Colonial in One v j ew . ( ^, ter Herdman.) 



B 



