AOKAJ^IA (aMFHIOXUS). 



309 



Fig. 17s.— Development of a Tunicate. 



A, Larva of Botrylhis, gi'eatly enlarged: a, processes for attachment; h, 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. », Diagrammatic cross-section of the tail : p, p, fins ; 

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



In Ampkioxus (fig. 179) we have a permanent dorsal nervous 

 system and notochord, this latter being an elastic cartilaginous 



^ /i [r P 



Fig. 179.— The Lancelet (^mpAzoarus lanceolatus). 



0, Mouth ; h. pharynx ; g, stomach ; h, liver ; i, intestine ; a, anus ; n, notochord ; 

 /, fln-ray.s ; jj, abdominal pore. (Nicholson.) 



