CHORDATA 



245 



but is drawn in by ciliary action, as in ascidians, lamelli- 

 branch molluscs, and sponges. The water after having 



Fig. 103. Ciona intestinal on side of rock 

 Natural size 



passed the branchia passes into an atrial chamber, as in 

 the ascidians. 



It has a notochord. that incipient form of " back-bone," 

 as have the ascidians and the embryos of vertebrates, a 

 spinal cord, but no brain. A pigment spot at the anterior 



