158 SAKYO KANDA. 



side. When both MgCl 2 and MgSO 4 were left out at 23 C., 

 those larvae which were at the bottom of the negative side con- 

 stituted about 40 per cent, or more, whereas they were about 30 

 per cent, or more with elimination of either MgCl 2 or MgSO alone. 

 As has already been seen, the addition of magnesium chloride or 

 sulphate to the natural sea-water had no negativating effect on 

 the heliotropism of the larvae. On the other hand, the addition 

 of sodium or potassium chloride had such effect. The fact that 

 magnesium and calcium chlorides seem to act as a positivating 

 component in the artificial sea-water as well as in the natural 

 sea-water is therefore clear, whereas potassium and sodium chlor- 

 ides act as negativating ones. In other words, magnesium and 

 calcium chlorides act in antagonizing the negativating effect of 

 sodium or potass'um chloride, or of both, although magnesium 

 cannot antagonize the toxic action of the latter salts as calcium 

 chloride can do, since the larvae could not remain active and live 

 long in calcium-free artificial sea-water. 



7. Effects of Alcohols. 



In narcotising Arenicola larvae, Lillie used many narcotics. 

 Of alcohols, he found that ethyl alcohol had a negativating effect 

 on the heliotropism of the larvae. It will be seen in Table IV. 

 that all of the alcohols tested by the writer had more or less effect 

 in making the larvae negative to light. Difficulty was expe- 

 rienced, however, in getting uniform results in different series of 

 experiments when different stocks of alcohols were used; prob- 

 ably this variability was largely due to impurity of reagents. 



Just as Loeb has shown with copepods and Daphnia, it is ob- 

 vious from Table IV. that the higher the alcohol in the series the 

 greater negativating effect it had. This point will be considered 

 a little later. With the exception of two cases, the higher the 

 temperature the quicker and larger was the negativating effect 

 produced. That the larvae in the mixture of methyl or ethyl 

 alcohol and natural sea-water at room temperature (22) were 

 less negative than at a temperature five degrees lower (17) is 

 hard to understand. 



Acetone and two esters were also tested. The general features 

 of the results obtained with these narcotics were quite similar to 



