24 



PHYLUM TUNICATA (UROCHORDA). 



Fio. 18. Diagram illustrating the metamorphosis of the larva of Clavelina during and after 

 fixation (from Korschelt and Heider, after Seeliger). A Free-swimming larva. B Larva 

 just attached. C Older metamorphosed stage, ch notochord ; e atrial aperture ; ed in- 

 testine ; ep epicardium ; es endostyle ; / ectodermal fold ; ft duct of neural gland ; g ganglion ; 

 h heart ; hp adhesive papillae ; i mouth ; ks gill-slits ; p atrial cavity ; r trunk-ganglion ; 

 s partition wall of stolon ; sb cerebral vesicle ; ss cast cellulose tissue of tail ; st stolo prolifer ; 

 x larval tail degenerating. 



