These results confirmed his laboratory findings. He also discovered that older 

 oysters collected in the brackish water of Maurice River Gove where growth is 

 extremely slow, when placed in the experimental square with younger oysters, 

 proved conspicuously more attractive to drills than the younger oysters. He ex- 

 plains that in the salty water on the flats of Delaware Bay growing conditions are 

 more favorable than in the Maurice River Gove, and Cove oysters when trans- 

 planted to the flats were stimulated to rapid growth and a high rate of metabolism, 

 a state characteristic of young oysters; Urosalpinx reacted to the older oysters as 

 though they were very young oysters. These studi.es suggest that the metabolic 

 rate of an oyster is more important than age in determining the degree of attract- 

 iveness of substances released by oysters , Haskm concludes that chemical 

 attraction plays a dominant role in food selection by Urosalpinx. 



Sizer (1936) demonstrated experimentally that drills are also attracted to 

 oysters in deep water . He placed drills at one end and oysters at the opposite 

 end of a cage and lowered it onto the bottom of Delaware Bay . During 24 hours 

 most of the drills moved onto the oysters . He states that the drill attracting 

 substance is probably a product of active metabolism which may be present in ex- 

 cretions and increases in concentration toward the oyster. The fact that a watery 

 suspension of macerated oyster meats or excised meats from freshly opened 

 oysters were inadequate in bringing about orientation of the drill, led him to state 

 that the attracting substance is elaborated by the living oyster and does not occur 

 to any appreciable extent in dead tissues . 



In large scale drill trapping operations m Delaware Bay Stauber (1943) 

 chose young oysters from the brackish waters of tributary tidal rivers for use 

 as bait because of low cost and ease of handling, and inadvertently selected bait 

 which competed in attractiveness with oysters of all ages on the Delaware Bay 

 oyster grounds , In pilot tests two to three month old spat from the intertidal Cape 

 Shore flats was also shown superior in attraction to older oysters, but did not 

 prove practical bait on other grounds , 



In both field and laboratory experiments Haskin found that three times 

 as many drills were attracted to summer old oysters as to Mytilus edulis. The 

 size and age of the mussels were not recorded Since drills respond differen- 

 tially to substances given off by oysters of different ages, they may respond in 

 a similar manner to other food animals . The reported preference of drills for 

 prey species other than oysters in some regions (Pope, 1910-11; Federighi, 

 1931c; Engle, 1935=36; Galtsoff et al., 1937; Cole, 1942; Stauber, 1943) may 

 indicate a more pronounced attraction to the ectocrines of these species than to 

 those of the oyster at the time of predation. Cole (1942) in explaining the lack of 

 attractiveness of mussels to drills in the River Blackwater, England, where 



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