1 62 PHYLUM CHORD AT A 



The upper limb is formed by the intestine, which passes to the 

 base of the excurrent siphon, where it ends with the anus. Find 

 these organs. 



The Reproductive System. Molgula is hermaphroditic. The 

 sexual organs consist of a pair of large hermaphroditic glands, one 

 of which is seen on each of the lateral sides of the body. A short 

 duct runs from each gland to the base of the excurrent siphon. 

 On the left side the duct will be seen alongside the posterior end 

 of the intestine ; find it. 



The Circulatory System. On the right side of the body beneath 

 the hermaphroditic gland will be seen the heart in its pericardium. 

 It is a muscular sac from each end of which proceeds a large blood 

 vessel. The vessel leaving the ventral end (at the observer's right) 

 is called the cardiobranchial vessel; it passes along the mid- 

 ventral side of the pharynx, beneath (external to) the endostyle, 

 and gives off branches which run transversely along the pharyn- 

 geal wall. The vessel leaving the dorsal end of the heart is called 

 the cardiovisceral ; it breaks up into numerous branches, which 

 ramify among the viscera and other parts of the body. From the 

 viscera the blood is collected again in a vessel called the viscero- 

 branchial, which passes along the mid-dorsal pharyngeal wall and 

 gives off transverse branches. 



The heart of tunicates is peculiar in that its pulsations change 

 the direction of the flow of the blood alternately from the cardio- 

 branchial to the cardiovisceral vessels, and back again. The con- 

 traction of the heart is of a peristaltic nature ; it passes from one 

 end to the other of it for a short time ; then after a short pause 

 the contraction is renewed, the peristaltic motion beginning at 

 the opposite end and driving the blood in the opposite direction. 



The Nervous System. About halfway between the two siphons, 

 embedded in the mantle beneath the dorsal surface of the animal, 

 lies a small ganglion from which nerves radiate. No organs of 

 special sense are present, except the tentacles and minute eyespots 

 at the incurrent and excurrent openings. 



The Excretory System. Beneath the heart is an elongated, vesic- 

 ular organ which is the single, unpaired kidney ; it is ductless. 

 Beneath the ganglion above mentioned is a small, glandular organ 



