2950 THE SEA SQUIRTS OR ASCIDIANS 



and the branchial chamber is simply an elongated pharynx, with two openings on 

 the lower surface, which correspond to the gill slits, and are well furnished with 

 cilia. The nervous system consists of a large ganglion placed in the anterior part 

 of the dorsal surface, followed by a long chord, provided with smaller ganglia, and 

 extending backward over the intestine to reach the tail, where it runs along the left 

 side of the skeletal axis. The intestine itself is situated behind the branchial cham- 

 ber, and the vent opens on the inferior or ventral aspect of the body in advance of 

 the gill slits. Neither budding, metamorphosis, nor alternation of generations takes 

 place; and the reproductive organs are situated at the hinder end of the body. The 

 group comprises only the single family Appendiculariida , which contains five genera, 

 the names and characteristics of which it will be unnecessary to mention. 



