MOLGULA MANHATTENSIS 261 



gland opens into the pharynx. The opening is surrounded by the 

 ciliated ridge called the vibratile tubercle. 



Circulatory system. The heart is an elongated organ situated 

 in the pericard on the right side of the animal between the right 

 reproductive gland and the kidney. It has no valves and the 

 direction of its peristaltic pulsation alone controls the direction 

 of the blood-current. It is a remarkable fact characteristic of 

 Tunicates that the direction of the pulsation and with it that of 

 the blood-current, changes periodically. The blood flows in both 

 cases out of the heart into the vascular sinuses and returns to the 

 heart by way of the opening opposite to the one by which it left 

 it. Although the sinuses are lacking a wall of their own, so that 

 the blood circulation is an open one, yet they are more or less 

 highly differentiated and almost play the role of real blood- 

 vessels. The most important among them are the ventral sinus, 

 the pericoronal sinus, and the branchial sinuses. The blood is 

 colorless and contains amcebocytes. 



Nervous system. The nervous system consists of a simple 

 ganglion situated below the adneural gland between the two 

 siphons. Special sense organs are lacking. 



Reproductive system. Molgula is a hermaphrodite. It 

 has a pair of ovaries and a pair of testes. The ovary and 

 testis of the same side of the body are so closely applied to each 

 other that they produce the impression of a single gland. Never- 

 theless each ovary has its own oviduct and each testis its own 

 sperm duct. The latter is a much thinner tube and runs in con- 

 tact with the corresponding oviduct. The glands themselves are 

 situated on the sides of the animal, those of the left side in the 

 loop of the intestine, those of the right side above the heart. 

 The genital openings are situated in the cloacal chamber some- 

 what above the anus. 



Instructions 



i. Place a Molgula in a dissecting tray with water, with the 

 anterior siphon directed away from you and the posterior siphon 



