TUNICATES OR ASCIDIANS AND LANCELETS II9 



Amphioxushas a notochord, but no definitely recognisable 

 heart. Water flows in at the cilia-fringed mouth, passes 

 over the sixty pairs of gill slits, and exits by an opening 

 under the undersurface. Like the Sea Squirts, it feeds 

 chiefly on Diatoms and in swimming can reverse as easily 

 as it travels forwards. The minute transparent egg, laid 

 in the late summer, hatches in about eight hours, the young 

 having the mouth sealed up for the first twelve hours or 

 so after hatching. The Lancelet is usually found on a 

 sandy or gravel bottom just beyond low tide limit. 



