MUSEUM OF COMPARATIVE ZOOLOGY. 



297 



appendages include all the organs of a tunicate animal, with the ex- 

 ception of the nervous system, the heart, and the reproductive organs. 

 Nervous System. — The nervous system is situated within the body 

 cavity, and is attached to the inside of the outer tunic between the 

 two external openings (Figs. 1, 3, 24, and 33, v). 



Auult solitary Salpa ; haemal view : a, test; 6, outer tunic; c, wall of branchial sac ; e, bran- 

 chial aperture; /, muscular girdles ; ft., branchial cavity; k, peripharyngeal ridges j m, en- 

 dostyle ; n, gill ; nil, nucleus ; r, heart ; u, chain of young males. 



The Heart. — The position of the heart varies greatly, but it is usually 

 found near the digestive organs (Figs. 1 and 3, r), and in all Tunicates 

 its motion is periodically reversed. 



The Reproductive Organs.- — These are usually placed upon or near 

 the intestine, and their external openings are near the anus. 



We are now prepared to consider the special modifications presented 

 in the organization of Salpa. 



