ACRANIA (AMPHIOXUS). 



279 



Fig. 145.— Development of a Thnicatb. 



A, Larva of Botrylhis, gi-eatly enlarged: a, processes for attachment; b, primitive 

 cells from which digestive organs develop ; d, eye-spot ; e, entrance to branchial sac ; 

 /, external test; g, large cells forming central axis, b, Portion of tail, enlarged: h, 

 central axis, c, Another larva, d, Diagrammatic cross-section of the tail : -p, p, fins ; 

 /i, central axis ; g, cellular, and/, external sheath. (Nicholson.) 



In Amphiox7j,s (fig. 146) we have a permanent dorsal nervous 

 system and notochord, this latter being an elastic cartilaginotis 



^ A o- P 



Fin. 146. — Thi-: 1jxvcei.et (A mpMoxus lanceolatus). 



0, Mouth ; b, pharynx ; g, stomach ; /t, li^'er ; i, intestine ; a, anus ; 

 /, fin-rays ; p, abdominal pore. (Nicholson.) 



