132 
C. Kenneth Dodd, Jr. 
margin apparently represents the limit to which the pond fills during 
periods of maximal rainfall. Tadpoles remained in the pond and were not 
observed in any of the small pockets of water located in the margin. 
Five study quadrats were selected and photographed with Kodachrome 
64 slide film using a Nikon F camera with a 55 mm micro lens. A one 
meter ruler was placed at the top of each area photographed to insure 
uniformity of quadrat size; each quadrat measured 25 x 40 cm (see Fig. 1 
for location of quadrats). The camera was hand held directly over the 
area to be photographed, in such a way as to assure that the film plane 
was parallel to the surface of the water and the scale of reference. If this is 
not done the resulting shift in parallax could cause a scaling problem, 
thus affecting area, and therefore density, estimates. Care was taken to 
insure that movements of the observer and placement of the meter ruler 
did not disturb the tadpoles and cause them to change their position. 
Each slide was enlarged to a 17 x 25.5 cm print and the 25 x 40 cm 
quadrat was marked off (Fig. 2). A clear plastic sheet was overlain on the 
photograph and tadpoles marked onto the sheet as they were counted. 
Thus, both the exact position and number of tadpoles could be scored for 
each quadrat. 
