AMPH1OXUS. 



441 



Skin. The epidermis consists of a single layer of cylin- 

 drical cells. Some of them project slightly from the surface, 

 and are connected at the base with nerve fibres. These are 

 sensory cells, and may be compared to the cells of the 



sp.c. 



tick. 



- in. 



a.c.f. 



Ph. 



air. 



FIG. 217. Transverse section through pharyngeal region of 

 Amphioxus. After Ray Lankester. 



sj>.c. , Spinal cord ; nch., notochord, beneath which lie the two dorsal 

 aortic ; ;., myotome ; a.c.f., atrio-coelomic funnel, opening 

 into sub-chordal coelom ; C., caecum; G., a genital sac with 

 ova ; nip., metapleural fold ; atr., atrial cavity ; Ph., pharynx, 

 with dorsal and ventral grooves, and bars between gill-slits. 

 Note in the primary bars and in the ventral groove the small 

 coelomic spaces. The ectoderm is dark throughout. 



lateral line in fishes and tadpoles. Here, however, they 

 are scattered over the surface of the body, though especially 

 abundant on the buccal cirri. The epidermis lies upon a 

 thin layer of clear cutis. 



Beneath this there is a layer of fine tubes, which unite in a longitudinal 



