PHARYNX. 



11 



f- 



neighbouring papillae 

 (Fig. 8). In this way 

 internal longitudinal 

 bars, connected to the 

 transverse bars and 

 extending the whole 

 length of the pharynx, 

 are often formed (Fig. 

 9 A). At the points 

 where the internal 

 longitudinal bars are 

 connected to the trans- 

 verse bars, small papil- 

 lae are often found 

 projecting into the 

 pharynx, and horizon- 

 tal membranes are 

 often present along 

 the transverse bars, 

 connecting these papil- 

 lae (Figs. 10 and 11). 



The stigmata vary much in form. They may be circular, oval, slit- 

 like, or spirally coiled. Their long axis is generally parallel to the long 

 axis of the animal. In a few, e.g. Boltenia elegans, Cynthia rillosa, it is 

 transverse. In a few deep-sea forms (Culeolus, Fungulus, Bathyoncus, 

 Pharynr/odictyon) the stigmata are large and square and there are no longi- 



FIGS. 9 and 10. A Part of pharynx of Ascidia from inside. 

 B Transverse section of the same. r transverse bar ; 

 cd connection of internal longitudinal bar to transverse 

 bar ; Jim horizontal membrane ; il internal longitudinal 

 bar ; / fine longitudinal bars ; tr transverse bar ; p, p' 

 papillae ; sg stigma (from Herdman). 



A 



B 



b 



c 



FlG. 11. Structure of pharyngeal wall of Ciona intestinalis (from Vogt and Yung). A from 

 within. B from outside, a internal longitudinal bar ; b transverse bar of the first order 

 c, g transverse bar of the second order ; d papillae projecting into cavity of pharynx from 

 the internal longitudinal bar ; e transverse bar of the third order ; /, /' stigmata. 



