54 



VERTEBRATE ZOOLOGY 



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, adh, adhesive 

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

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

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

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



