THE LANCELET 



333 



ventral wall is formed by a longitudinal bar, known as the 

 endostyle, with which the lower ends of the gill bars are 



,- t mym. 



-nch. 



d.i. 



■pr.al. 



Fig. 241. — A transverse section of Amphioxus in the region of the 

 intestine. 



c.s., Connective tissue sheath of the notochord ; coeL, caelom ; d.ao., dorsal aorta ; 

 d.f.r., dorsal fin ray ; d.r., dorsal root ; int., intestine ; mym., myomeres ; n.c, 

 nerve cord ; nch., notochord ; fir. at., backward prolongation of the atrium ; s.i.v. t 

 subintestinal vein (here represented Ivy several vessels) ; v.f.r., ventral fin ray. 



fused. This bears a groove lined by ciliated cells with two 

 longitudinal bands of gland cells on each side. These cells 

 secrete mucus which is passed outwards by the cilia. At the 



