frequently later. Stauber conducted his experiments at winter temperatures 

 consistently below 20° C which fluctuated roughly with those out of doors, while 

 previous experimenters performed their experiments only during the summer 

 months at temperatures usually well above 20 s C. Stauber soon determined that 

 at winter temperatures drills could survive for considerable periods of time under 

 less saline conditions than previously reported. Drills were able to attach to the 

 sides of the containers in salinities as low as 7 o/oo though they later died under 

 these conditions . Half of the drills were able to attach after 26 days of exposure 

 to 8 o/oo, after 121 days to 9 o/oo ; and 248 days to 10 o/oo. Without food one 

 drill was capable of attachment in 8 o/oo on the 136th day, in 11 o/oo on the 234th 

 day, and in 9 o/oo on the 344th day. Two of the original drills in one of these 

 dishes were still alive and capable of attachment and movement after more than 

 19 months in water of 10 o/oo, 



Stauber then instituted a series of 6 experiments to test more carefully 

 the effect of dropping temperatures on drill survival in low salinities. These ex- 

 tended from August to March and were conducted at temperatures roughly parallel- 

 ing outdoor winter temperatures . Lots of 10 drills each, a total of 60 drills per 

 experiments were confined in dishes with saline water of 6, 7, 8, 9, 10, and 11 

 o/oo. The results of these exposures are indicated in Table 10. Though not 

 reported, it is assumed that the temperature of the water in the experiments during 

 the second 30 day period was considerably lower especially in the experiments 

 performed in the late summer and fall. Stauber concludes that at lower water 

 temperatures he obtained not only greater early recovering and attachment of the 

 drills but also greater ultimate survival and resistance to the effects of the un- 

 favorable conditions . 



Further experimentation was necessary to demonstrate whether drills would 

 survive conditions duplicating those in nature during low temperatures when periods 

 of low salinities caused by excessive rainfall are followed by periods of higher 

 salinity. At temperatures prevailing outdoors in early spring Stauber placed 50 

 drills each in large aquaria containing aerated water of the following salinities: 

 0, 1, 2, 3, 4, 5, 6, 7, 8, and over 15 o/oo. On successive days he removed ali- 

 quots of drills and placed them in water saltier than 15 o/oo. The number of drills 

 recovering sufficiently from this double treatment to attach to glass in the aquaria 

 and the time of exposure required to kill the drills in each salinity, are given in 

 Table 1 1 . Stauber' s experiments very clearly demonstrate that in the field as well 

 as in the laboratory the rate of destruction of drills by low salinities will be 

 determined by the salinity of the water, the prevailing temperatures, and the 

 duration of the conditions . Stauber (1943a) has introduced a graphic means of 

 presenting salimty.in an estuary, based on Delaware Bay, which indicates the 

 variations and extremes which can occur . A recording of these is important in 



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