238 CHORDATA 



the ventral end of the heart. The frequent reversal of the 

 current can be readily seen both in the heart and in the ves- 

 sels. 



The relation of the parts will be more clearly understood 

 if a second large specimen is dissected as follows: with 

 scissors cut off the atrial siphon, thus exposing the atrium; 

 then similarly remove by a single cut the oral siphon, to- 

 gether with the anterior end of the pharynx (the piece thus 

 cut off should contain the ganglion, dorsal tubercle, peri- 

 pharyngeal bands, oral tentacles, anterior portion of the en- 

 dostyle, dorsal lamina, etc.). 



Make drawings that will show the structure. 



Hunter: Notes on the Heart Action of Molgula manhattensis. Am. 



Jour. Physiol., 10, 1903. 

 Kingsley: Some Points in the Development of Molgula. Proc. Roy. 



Soc. Nat. Hist., 21, 1883. 

 van Name: Simple Ascidians. Proc. Bost. Soc. Nat. Hist., 34, 1912, 



PEROPHORA 



This ascidian occurs on piles and other submerged mate- 

 rials, 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 very much like minia- 

 ture 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 separate tunics. 



3. Study the stolon with its flattened epicardiac tube. 

 This tube is derived from the branchial sac and is accord- 

 ingly endodermic. 



