64 LABORATORY DIRECTIONS IN 



can best be seen in a portion of a single lamella (half of one 

 gill) mounted in Ringer's solution between slide and cover- 

 glass, and studied with high magnification. Sketch a little 

 of the gill surface showing the cilia and their relation to the 

 openings. 



2h. Tear apart the two lamellae of which each gill is composed, and 

 note that these enclose vertical tubes which extend from the 

 free edge of the gill to its attached dorsal edge. With scis- 

 sors cut thick cross-sections of the gill to show the lamellae 

 and tubes. Draw a small portion of the cut edge. 



2i. Put a probe into the exhalent siphonal opening. It enters a 

 channel above the attached edge of the gills. Cut through 

 the gills by drawing a knife along the probe, and explore the 

 gill chamber into which the vertical tubes from the gills open. 



2j. Trace the course of the water from the inhalent siphon into the 

 mantle cavity, thence through the gill tubes, and out at the 

 exhalent opening. 



2k. How do you suppose the animal breathes? Gets its food? 

 Removes the waste products of respiration, digestion, and 

 excretion? 



21. Examine a specimen containing glochidia and note how the ex- 

 panded spaces between the gill lamellae serve as brood pouches. 



2m. Examine some of the glochidia of Anodonta in water under a 

 low magnification. Sketch to show: 



1. The triangular valves of the shell. 



2. The large tooth at the apex of each valve. 



3. The strong adductor muscle. 



4. The thread-like byssus (of uncertain function). 



2n. By reading one of the following references, or by consulting the 

 instructor, learn how the glochidia attach themselves to fish 

 and are distributed by them. 



LEFEVRE, G. and CURTIS, W. C., 1912. Studies on the Reproduc- 

 tion and Artificial Propagation of Fresh-water Mussels. Bull. 

 Bureau of Fisheries, 30: 107-201. 



NEEDHAM, J. G. and LLOYD, J. T., 1916. The Life of Inland 

 Waters. Comstock Publ. Co. See pp. 287-292. 



BAKER, F. C., 1916. The Relation of Mollusks to Fish in Oneida 

 Lake, Tech. Publ. No. 4., N. Y. State College of Forestry at 

 Syracuse University. See pp. 219-223. 



2o. Examine the demonstration of towings made with a fine mesh 

 Birge cone net from the sandy shoal habitat where the mussels 

 were collected. In general, what kinds of minute organisms 

 occur there? Then: 



