180 CHORDATA. 



PEROPHORA. 



This colonial simple ascidian occurs on piles and other sub- 

 merged materials, and is commonly attached by branching 

 stolons to seaweeds, simple tunicates, or other sessile animals. 

 Material should be quite fresh for satisfactory study, and should 

 be carefully handled to avoid crushing. Study in a watch-glass 

 of sea-water (or support the cover-glass), with a low power of the 

 microscope. 



1. Notice that the individuals are essentially very much like 

 miniature Molgulas. Identify as many of the organs that were 

 seen in Molgula as possible, noting the differences. 



2. The form illustrates the type (Clavelinidae) in which a 

 colony is formed by budding from a stolon, but in which the 

 individuals~retain their identity to a great degree and have sepa- 

 rate tunics. 



3. Study the stolon with its flattened epicardiac tube. This 

 tube is derived from the branchial sac and is accordingly endo- 

 dermic. 



4. Study buds of various sizes and see how the inner vesicles 

 arise from the epicardiac tube. 



5. Try to make out the entire course of the circulation of the 

 blood. Notice especially the heart, branchial vessels, vessels of 

 the mantle, and the circulation of the stolon. Watch the pulsa- 

 tions of the heart and see the reversal of the blood-current. Is 

 the heart-beat synchronous in different individuals? What part 

 of the blood is colored ? 



6. Study the action of the cilia in the gill clefts. 

 Drawings of a colony and of an individual are desirable. 



Lefevre: Budding in Perophora. Jour. Morph., 14, 1898. 



BOTRYLLUS. 



The small, radially arranged colonies of this composite ascidian 

 are common on eel-grass, from which they may be separated by 

 means of a knife, and studied alive in a watch-glass with a low 



