PELAGIC TUN1CATES 



7i 



Fig. 39. Doliolum, gonozooid. 



I, inhalent aperture; 2, ciliated pit; 3, ganglion and nerves; 4, pharynx; 5, mantle; 



6, sense-cells, 7, exhalant aperture; 8, ovary; 9, intestine; 10, heart; 11, endostyle; 



12, testis; 13, ciliated groove. (After Neumann.) 



atr 



muse 



ats 



an 



br.s 



Fig. 40. Cyclosalpa affinis, oozooid with chain of five wheels of blastozooids. 

 an. anus; atr. atrium; at.s. atrial siphon; hi. blastozooid with egg; br.s. branchial siphon; en. endo- 

 style; gn. ganglion; gr. gill ridge; ht. heart; muse, muscle ring; ph. pharynx; s. stomach. 

 ( X £ modified. After Ritter and Johnson and Berrill.) 



generations. In Doliolum the ascidian tadpole develops into a mother 

 or nurse zooid (oozooid). This by budding gives rise to a string of 

 daughter zooids, which it propels along by its muscles. The daughter 

 zooids are of three types: (i) sterile, nutritive, and respiratory indi- 

 viduals, the trophozooids, permanently sessile on the parent; (2) 

 sterile nurse forms, which are eventually set free (phorozooids); (3) 

 sexual forms (gonozooids, Fig. 39), nursed and carried by the phoro- 

 zooids until sexually mature, when they also break loose. 



In Salpa the sexual form (blastozooid), produces only a single egg, 



