ACEANIA (AMPHIOXUS). 



279 



Pig. 145. — Development of a Tunicate. 



A, Larva of Botryllus, greatly enlarged : a, processes for attachment ; &, 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 ; 

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



In AmpMoxus (fig. 146) we have a permanent dorsal nervous 

 system and notochord, this latter being an elastic cartilaginous 



J ) 



i k ^ f ' "^ 



Fig. 146.— The Lancblbt {^AttupMAxmB lariceolatm). 



0, Mouth ; b, pharjTix ; ■ g, stomach ; h, liver ; i, intestine ; a, anus ; 

 /, fln-rays ; p, ahdominal pore. (Nicholson. ) 



7t, notochord : 



