A Simple Tunicate. 141 



cardiac, conveying pure blood to the heart along the ven- 

 tral trunk ; 2d, Cardio- splanchnic, conveying blood from 

 the heart to the viscera and other parts of the body ; 3d, 

 Splanchno-branchial) conveying impure blood from the 

 viscera, etc., through the dorsal trunk to the branchial 

 sac. 



The test is supplied with blood through vessels that leave 

 the main trunks near the heart. 



The Nervous System. The nerves from the ganglion 

 may be traced to certain sense-organs. The ocelli are sit- 

 uated around the oral and cloacal orifices. The tentacles 

 have already been noted. 1 



The Reproductive System.- The Tunicata are her- 

 maphrodite, though probably not self-fertilizing, as the ova 

 often reach maturity much earlier than the spermatozoa. 

 In Molgula the ovary and testis unite and form a pair of 

 hermaphrodite glands ; in other forms the glands may be 

 separate. Reproduction by budding is not infrequent. 

 This process may give rise to small colonies, the individuals 

 of which may have a common circulatory system. Such 

 Tunicates are called Social in distinction from the Solitary 

 Tunicates, of which Molgula is a type. 



1 For a long time the dorsal tubercle was supposed to function as a 

 sense-organ, and was called the olfactory tubercle. It is now known 

 to be the funnel-shaped extremity of a ciliated duct, leading from 

 the neural gland. It has been compared to the pituitary body of 

 Vertebrates. 



