456 SUB-PHYLUM UROCHORDA OR TUNICATA. 



ganglionic mass above the mouth, and a dorsal nerve-cord extending 

 backward from this into the tail, where it is furnished with other 

 ganglia. In connection with the cerebral ganglion there is a pigment 

 spot, an otocyst (auditory ?), and a tubular process communicating with 

 the pharynx, and corresponding to the -sub-neural gland and the ciliated 

 duct of other Tunicates. We have already noted the simple structure 

 of the pharynx, which has but two gill-slits communicating directly with 

 the exterior. The same simplicity of structure is observable in the 

 heart, which is without any associated vessels. The hermaphrodite 



FIG. 247. Anatomy of Appendicularia. After 

 Herdman. 



t J.0., Sense organ ; />r., branchial aperture ; /., dorsal tubercle ; 0/., 



otocyst; .., nerve ganglion \ pp.> peripharyngeal band ; ., 

 nerve-cord ; as., oesophagus ; st., stomach ; ov., ovary; tes., 

 testes ; z., intestine ; /*., heart ; u., urochord, cut at u'. ; n.g '., 

 n.g"., nerve ganglia of tail ; m. t muscle Land; #//., tail cut 

 through J a., anus ; a/., one of the atrial apertures ; end., endo- 

 style. 



reproductive organs lie posteriorly, and open to the exterior by a 

 very fine duct on the dorsal surface. As contrasted with Salpa and 

 Doliolunii the animals are protandrous, and not protogynous. The 

 development is unknown. 



Classification. 



Order i. LARVACEA 



Free-swimming, pelagic, and solitary forms provided with a large 

 locomotor tail containing a notochord. The pharynx opens to the 



