54 



VERTEBRATE ZOOLOGY 



jned I sens.ves 



or 



jil stiff e-Tvd. 



Fig. 25. — Diagram showing the metamorphosis of the free-swimming "tad- 

 pole" larva of an Ascidian into the sessile or fixed adult condition. A, stage of 

 free-swimming larva; B, larva recently fixed; C, older fixed stage, od/i, adhesive 

 papillte; atr, atrial cavity; cil. gr, ciliated diverticulum, becoming ciliated funnel; 

 end, endostyle; ht, heart; med, nerve cord of trunk; n. gn, nerve ganglion; now, 

 notochord; or, oral aperture; red, rectum; sens.ves, sense vesicle or brain; stig, 

 stigmata; stol, stolon; (, tail. (From Parker and Haswell, after Seeliger.) 



