because of the close systematic relation 

 of Ocine bra to Urosalpinx, it is prob- 

 able that their feeding processes are 

 similar. According to Carriker (1955), 

 Urosalpinx cinerea has a feeding proc- 

 ess which consists of a mechanical 

 rasping of the softer flesh of the prey. 

 The proboscis is extended through the 

 newly drilled hole and the radula tears 

 away bits of flesh with its sharp, 

 backward-pointed teeth. Flesh caught 

 on the radular teeth and transported 

 into the buccal cavity is neatly re- 

 moved by esophageal suction and then 

 carried by ciliary peristaltic activity 

 to the stomach. 



The precise mechanism by which the 

 Japanese drill differentiates between 

 species of prey is unknown. Sizer 

 (unpublished report)' , Galtsoff et aX» 

 (1937), and Federighi (1931) pointed out 



that Urosalpinx cinerea possessed an 



osphradium--an organ intimately con- 

 nected with the gills and generally 

 placed near their base. Urosalpinx 

 may possibly be attracted to the food 

 through the osphradium. Whether or 

 not this applies to Ocinebra is unknown. 



Water samples were taken when the 

 test animals were collected in the field 

 in order to observe changes in pH and 

 salinities to which the drills were 

 subjected in being transferred from 

 the field to the aquarium. The dif- 

 ferences were greatest when the drills 

 were brought in for Experiment I. 

 No literature has been published on the 

 pH tolerance level of Ocinebra. As for 

 salinities. Chapman and Banner (1949) 

 claim 22%o and above had little effect 

 on Ocinebra japonica, while salinities 

 below 12 %o were lethal. 



The average pH of the water through- 

 out this study was 7.32 (ranging from 

 7.00 to 7.52). Normally, the hydrogen 

 ion concentration of the water within 

 the recirculating system increases 

 over a period of time, depending on the 

 number and kinds of animals held in 

 the aquarium. 



2 Unpublished report by I. W. Slzer, 1936. Observations 

 on the oyster drill with special reference to its movement 

 and to the permeability of its egg case membrane. U. S. 

 Bureau Fisheries, Washington, D. C. 



When the pH approached 7.00, most 

 of the old water in the system was 

 drained out through the sewer, and new 

 water was pumped in fronti a reserve 

 supply. New water was introduced twice 

 during this study (August 20 and 

 November 12, 1957). 



The average salinity in the aquaria 

 throughout this study was 29.47 %o 

 (ranging from 29.19 to 30.03). The 

 salinity of the aquarium sea water 

 was found to decrease with time. It 

 was expected to increase, since a 

 certain amount of water evaporation 

 should have been expected. The de- 

 crease in salinity is probably due to 

 condensation of moisture from the 

 warmer air on the colder exposed sur- 

 faces of the tank where it can drop into 

 the system. 



ACKNOWLEDGMENTS 



The use of the marine aquarium 

 facilities at the College of Fisheries, 

 University of Washington, was indis- 

 pensable to this project. Dr. Allan C. 

 DeLiacy supervised the care and nnain- 

 tenance of experimental animals used 

 in this study. 



I am also grateful to Dr. Douglas G. 

 Chapman for his aid in experimented 

 design and statistical treatment; to Dr s. 

 James E. Lynch, Joseph A. Stern, 

 Richard Van Cleve, and Arthur D. 

 Welander for their valuable comments; 

 to Dr. Albert K. Sparks for his help 

 in editing this paper; to David C. Mc- 

 Millin and Nat A. Waldripfor providing 

 the test animals; to Ralph Riley for 

 salinity analyses of sea water; and 

 finally, to Dr. Frank G. Lowman for 

 his help with control of the electrical 

 lighting system. 



SUMMARY 



1. To obtain a group of test animals 

 that were fronn the same environ- 

 nciental surroundings, all test ani- 

 mals were collected in a single 

 locality within a radius of 150 

 yards. 



25 



