76 



BALANOOLOSSIDA. 



apertures are, except in Ptychodera and Stereobalanus canadensis, 

 tubes, which lead outward to open externally by the branchial 

 pores placed in the branchial groove on each side of the middle 

 dorsal line. The internal openings (gill-slits) are U-shaped, the 



1011 



1 .0. 111. aliifsoliiiltniiis iiinnitiix. transverse section through the lirauchuil region, .-oinewliat 

 diagrammatic (alter Spem-el in mi Lang). / dorsal nerve eord ; 2 dorsal blood-vessel: 3 bran- 

 chial (submedian) groove ; /ectoderm; .j^<ma<i ; 6 longitudinal muscles of body-wall; 7 vi-n- 

 tral vessel ; ,\ ventral ner\e cord ; 9 trunk eneloiii ; 111 yrnital pure ; 11 branchial pore ; ;.' 

 tongue bar containing extension of trunk eoeimn; /.; |iar:iiiranchi<al ridges; 14 primary or 

 septal liar. I.e. portion of wall of pharynx interveniiiii bet ween two successive ch-t'ts ; 1,~> 

 dorsal P ar t "I <-avil\ oi pharynx; Hi h\ pobraiu-liial groove of pharynx, in this region 

 very largely developed. 



dors il margin having a tongue-like projection, forming a tonguc- 

 1 r (Figs. 60, 62) as in Amphioxus. This loads into a pouch 



canal \vith the food to escape. On this view, the skin, which contains a 

 rich plexus lit' liliiud \-(.-sscls. vvmild art as tlu> main nroan of respiration. 



