MOLGULA 137 
appear as light-colored bands in the pharyngeal wall. Find 
and trace a white or cream-colored line extending in the mid- 
ventral line from the base of the incurrent siphon to the opposite 
side of the body. This is the endostyle; it is a ciliated and 
glandular groove which lies between two folds in the mid- 
ventral wall of the pharynx; it extends the length of that 
structure and ends posteriorly near the opening of the pharynx 
into the @sophagus. Find this point. The cesophagus is short 
and communicates with the stomach, and these two divisions 
form the lower and thicker limb of the S-shaped digestive 
tract. 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 cardio-branchial 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 pharyngeal wall. The vessel leaving the dorsal end of 
the heart is called the cardio-visceral ; 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 
