52 MOLLUSCOIDA. 



10. Put a small living branch in a drop of sea-water under 

 a supported cover-glass and see if any of the zooids will expand. 

 If any do expand they may be examined, with a high power, 

 to good advantage. 



Study specimens that have been killed while expanded. 

 Stain with iodin, wash in water, mount in glycerin, study with 

 a high power. Find the retractor muscles, the funieulus, germ 

 cells, and, if possible, the shape of the alimentary canal. As 

 the alimentary canal bears a definite relation to the position 

 of the zooid on the branch, its shape can be readily determined 

 only when the branch happens to be twisted so the zooid is 

 to be seen in side view. 



Make a drawing showing the structure. 



If time permits it will be desirable to examine an incrusting 

 form to determine its method of branching and the way in which 

 the cups are closed. 



PLU MAXELL A. 1 



If the zooids of this fresh-water form will expand in a watch- 

 glass of fresh water, notice the shape of the lophophore and the 

 position of the epistome. In such a specimen the ganglion may 

 be seen as a rounded mass just beneath the lophophore, between 

 the mouth and the anus. Study the statoblasts with a micro- 

 scope. 



BRACHIOPODA. 



TEREBRATULINA. 



Examine specimens on the demonstration table and notice : 



1. Shell. The difference in the size and shape of the two 

 valves and their position in relation to the body. How are the 

 valves articulated ? How are they opened ? 



2. Peduncle. Its position. What is its use ? 



1 Slices of the large gelatinous form, Pectinatella, placed in watch- 

 glasses of fresh water, make very satisfactory objects for study, as the 

 zooids will soon expand, and they are then in the best possible position for 

 study. 



