temperature of only 1.0.9 C Gibbs (Stauber. 1950) observed cases of ovi- 

 position in Narragansett Bay Rhode Island, in 12 feet of water at temperatures 

 as low as 11 , 1"C . In England Cole (1942) finds that spawning begins each year 

 when the temperature of the water reaches 12-13 °C. Adams (1947) notes that 

 in Canadian waters Uro sa lpinx spawn at 20°C. 



In laboratory experiments with lots of drills from various regions Loosan- 

 off and Davis (1950-51) observed that egg laying began at 12°C in Rhode Island 

 drills,- at 15 "C in those from Long Island Sound, New Jersey, and North Carolina- 

 and at 19°C in drills from Virginia and South Carolina (Table 14) , 



Tolerance to extremes of temperature 



U. cmerea is apparently an eurythermal organism. According to Sizer 



(1936) high temperature regions do not prove to be a barrier to its distribution in 

 New Jersey for it is very active in the shallow waters along the Delaware Bay 

 where temperatures may rise above 30° C for considerable periods of time.. 



At the other extreme of the temperature range ; the drill appears to with- 

 stand low temperatures which apparently are lethal to some related drills Orton 

 and Lewis (1931) and Orton (1932) were able to record the relative abundance of 

 Uro salpinx and of two related drills, Ocenebra an d Nucella, and the associated 

 temperatures and salinities in the River Blackwater estuary, British Isles, during 

 the period 1928-1930. During the winters of 1926-1928 and 1930 temperatures of 

 the water did not fall much below 3.8*0. But during most of January and February 

 of 1929 the mean monthly temperature dropped 2,2 to 5.6°C below normal Two 

 day temperature means for January fell to a minimum of 0.4" C and for February 

 to -1.5'G. In the three year period 10, 852 drills were dredged from the lower 

 more saline grounds of the estuary where all three species of drills were normally 

 abundant „ Uro salpinx was* apparently unaffected by the cold of 1929 and its 

 numbers may have actually increased; Nucella suffered severe losses; and Ocenebra 

 was almost annihilated Orton lists the sustained low temperatures and associated 

 low salinities which came at the beginning of the cold period as the probable causes 

 of the heavy mortality. He notes that the distribution of Urosalpinx extends larther 

 up the estuary into less saline water than does that of the other two species, indicat- 

 ing that Urosalpinx is also more euryhaline than the related species. Galtsoff et al. 



(1937) observed Urosalpinx at temperatures as low as -3 & C and report no mortalities. 



Water Currents 



Federighi (1929, 1931c) in carefully executed laboratory experiments making 

 use of a celluloid trough and water currents of the turbulent type ; discovered that a 



75 



