ASCIDIA, 295 
Fig. 207.—TRANSVERSE SECTION OF LARVA OF ASCIDIAN. 
(After Van BENEDEN and JuLin.) 
Nerve Cord. 
Mesoblastic Sac, 
hypoblast, and a pair of lateral mesoblastic masses more or 
less broken up. 
This larva is characteristic 
of the Chordata though only 
found as a larva in the 
Atriozoa, being represented 
by an embryonic stage in 
Vertebrata. The further 
development of the Ascidian 
diverges from that of the next 
class. The larva becomes 
divided into a body and a 
tail, nearly all the notochord 
and mesoblast being carried. 
back into the tail (hence 
Urochorda), whilst the tail 
Fig. 208. —CHORDULA LARVA 
OF AN ASCIDIAN. 
(After KowALEVSKI1.) 
Neuropore. 
: _-Neural Tube. 
Dorsal view. 
Fig. 209.—AN ASCIDIAN TADPOLE. 
Brain. 
Neural Tube. 
Mesenteron. 
Notochord. 
A median section. 
