Figure 2.--Measuring the length of a Japanese drill. 



the mean were used to represent the 

 adult drill population. 



On the second day of the conditioning 

 period, drills needed for Experiment 

 I were selected at random from the 

 specified size group and painted for 

 identification with synthetic paint 

 (Speedtec Synthetic Finish). One color 

 was painted on the apex and another 

 color on the varices. Various color 

 combinations were made with silver, 

 yellow, red, and blue paints. Drills 

 for Experiment II were collected, 

 measured, and conditioned in an iden- 

 tical manner. 



The bay mussels, Manila clams, 

 Olympia oysters, and Pacific oysters 

 were measured in the plane of greatest 

 shell length. For each food species an 

 arbitrary size range around the mean 

 was selected to represent the most 

 available adult food population for the 

 drills. 



Size Grouping 



Table 1 represents the number col- 

 lected, miean lengths, "t" values, and 

 size ranges of animals used for Ex- 

 periments I and II. For each species 

 of test animal, a statistical "t" test 

 was conducted to determine if the 

 mean lengths of animals collected for 

 Experiments I and II were significantly 

 different. If a "t" value, evaluated at 

 the 5 percent level, revealed no signifi- 

 cant difference between mean lengths, 

 the same size ranges used in Experi- 

 ment I were used for Experiment II. 

 However, if a significant difference 

 was found between the mean lengths 

 of Experiment I and Experiment II 

 animals, the group for Experiment II 

 was selected around the second mean 

 rather than the mean of Experiment I. 

 The number of animals used in the 

 second experiment was nearly the same 

 percentage of those collected as in the 

 first experiment. 



Table 1. --Numbers, mean lengths, "t" values, and size ranges of test animals 



\J Percentages of samples are given only when the "t" values are significant, 



2/ (sign.) = significant difference between the mean lengths of the two samples at the 5% level, and 

 (not-sign.) = no significant difference. 



