156 SAKYO KANDA. 



this solution swam about at the bottom of the beaker. About 

 90 per cent, or more of the larvae were always positive to light. 



5. Effects of Hypertonic Sodium and, Potassium Chloride Solutions 



Added to the Artificial Sea-water. 



These effects were remarkable. In the mixture of 15 c.c. 

 m-NaCl and 35 c.c. of the artificial sea-water, about 90 per cent, 

 of the larvae became negative to light at about 20 minutes after 

 the treatment. Most of the negative animals stayed at the 

 bottom of the negative side of the beaker. In the mixture of 

 0.8 c.c. of m-KCl and 50 c.c. of the artificial sea-water, which 

 was the optimum proportion, about 75 per cent, of the larvae 

 became negative to light at about 30 minutes after the treatment. 



The mixture of 15 c.c. of isotonic NaCl and 35 c.c. of the arti- 

 ficial sea-water was also tested. It changed the reaction of about 

 85 per cent, of the larvae. In comparing these results with those 

 shown in Table III., it may be concluded that the effective order 

 of ions is variable as other environmental conditions are varied. 

 It is little wonder therefore that the order of ionic actions ob- 

 tained by different investigators is not always uniform. 



6. Effects of Elimination of Certain Salts from the Artificial Sea- 



water. 



By eliminating each separate component from the artificial 

 sea-water made up of six components, the specific role which 

 such component played on either positive or negative helio- 

 tropism of the larvae might be, the writer thought, in part under- 

 stood. 



First of all, NaCl solution was left out of the artificial sea- 

 water. Larvae transferred into the mixture without NaCl at 

 22 C., were practically all motionless immediately after the 

 treatment. Sodium chloride being the essential component of 

 the artificial sea-water as well as of the natural one, such result 

 should be expected, since the osmotic as well as the chemical 

 conditions are profoundly changed. 



According to Ewald, however, "leaving NaCl out of artificial 

 sea-water" "increases the negative and diminishes the positive" 

 heliotropism of the nauplii of Balanus perforatus which are 



