ASCIDIACEA FIXATION AND METAMORPHOSIS. 



375 



ft /" 



Pig. 173.— Diagram illustrating the metamorphosis of the larva of Clavdina during 

 and after fixation (mainly after Seeliger). A, free-swimming larva ; B, larva just 

 attached; (', older metamorphosed stage, ch, chorda; e, atrial aperture; e<l, in- 

 testine; ep, epicardial process; es, endostyle ; /, ectodermal fold ; fl, ciliated pit; 

 g, ganglion; h, heart ; hp, adhering papillae; i, branchial aperture; ks, gill-slits; 

 p, atrial cavity ; r, trunk-portion of the medullary tube ; s, partition-wall of the 

 stolon ; sb, sensory vesicle ; ss, the cast cellulose envelope of the tail ; st, stolo pro- 

 lifer ; .'•, the larval tail in course of degeneration. 



