mussels are relatively scarce, suggests that Uro salpinx may evolve a predilec- 

 tion for those prey which occur commonly in its immediate habitat. 



Cole (1942) could not establish that the drill is able to detect the presence 

 of food and move toward it. He placed English Urosalpinx in the center of a 

 wooden trough painted inside with pitch and filled with sea water . Young oysters 

 or barnacles were set at varying distances from the center toward one end of 

 the trough. During the experiments temperature ranged from 13 to 25° C, both 

 bright sunlight and shade were employed, and the water in the trough was not 

 moving. Under these conditions the drills moved at random, even when food was 

 as close as 35 cm, Two conditions of the experiment may explain the lack of 

 response of the drills to living food: the use of still water in which ectocrines 

 diffused slowly and possibly irregularly, and a possible masking of the ectocrines 

 by chemicals released by the pitch . 



Stauber (1943) has noted that confinement of prey in aquaria for extended 

 periods seems to reduce their activity and apparently their attractiveness to drills . 



Galtsoff in recent experiments (pers. com.) has contributed further informa- 

 tion on the detection of and movement of drills toward food . During the summer of 

 1954 he carried out 20 experiments in which 50 drills were placed in a large shallow 

 water tank about 16 feet long and 8 feet wide in which the water moved parallel to 

 the long axis of the tank at the rate of 1/2 cm./ sec . In a second set of experi- 

 ments 20 drills were placed in a wooden trough 10 inches wide and 16 feet long. 

 The water in this moved at the rate of 2 cm ./ sec A vertical partition divided 

 one end of each trough into two parts Adult oysters were placed on one side of 

 the partition and seed oysters on the other . Drills were placed in each trough at 

 the end opposite the oysters where they received water flowing past the oysters . 

 The results were consistent in showing that approximately 50% of the drills began 

 creeping toward the food. The remainder scattered about, sometimes climbing 

 on the walls of the troughs, and remained inactive. The path of the active drills 

 was a rather irregular spiral with many turns and circles . When approaching the 

 oysters, the majority of the drills oriented themselves toward the seed oysters. 

 The rate of crawling was inconstant and crawling was frequently interrupted by 

 periods of inactivity. The rate of crawling while the drills moved in a straight 

 line was about 1 cm. in 35 seconds. It is significant in terms of Cole's negative 

 results that when the water was shut off in Galtsoff" s tanks all the drills scattered 

 in different directions and none reached the food within 48 hours . 



As the drill approaches a living oyster to which it has been attracted Stauber 

 believes it may confirm the immediate presence of its prey by creeping to the ex- 

 current stream of the oyster and/or by the shell movements of the bivalve . Neither 



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