MOLGULA MANHATTENSIS. 165 



UROCHORDA. 



MOLGULA MANHATTENSIS. 



Specimens of this simple ascidian may be found attached to 

 old piles, associated with many other forms. In some localities 

 they may be so abundant as to practically incrust the piles, and 

 crowd each other out of shape. Examine such a mass and see 

 how different sized individuals are associated. Pull them apart 

 and see if there is any tissue connection between them that 

 would indicate a definite relation between neighbors. Do you 

 understand how the individuals get started in the places where 

 they are attached ? With a glass-bottomed pail you can see the 

 expanded individuals on the piles> but they can be more satisfac- 

 torily studied in small dishes of sea-water. 



1. Observe the contraction and closure of the two siphons 

 when the animal is irritated. 



2. Add a little powdered carmine to the water to determine 

 which is the incurrent or oral and which the excurrent or atrial 

 siphon. 



3. Ascertain the number of lobes at the extremity of each 

 siphon. Are pigment-spots present on the siphonal lobes? 



Certain organs are distinguishable through the tough tunic 

 which incloses the body. The endostyle in the mid-ventral line 

 of the pharynx or branchial basket will serve as a guide in orient- 

 ing the animal. Determine dorsal, ventral, anterior, right and 

 left aspects. 



Make a draining of an expanded animal. 



4. The tunic or test can be removed by cutting through it 

 with scissors, taking care not to injure the mantle or body-wall. 

 Enlarge the opening made in the tunic and strip it from the body. 

 Where is the tunic most firmly attached? Examine a small 

 piece of the tunic microscopically. Are blood-vessels ' visible 

 in it? Does it contain any cells? 



5. For further study use both fresh and preserved material 

 from which the tunic has been removed. Identify as many 

 organs as possible through the mantle. In a living specimen 



