152 



SAKYO KANDA. 



young ones. The sensitivity of the larvae to changes of medium 

 varied greatly according to their age. It was impossible to get 

 larvae uniformly young. This was the reason why one could 

 not get a reversal of all larvae treated even with the best agents. 

 There was always one or two per cent, of exceptions. Table I. 

 gives the summary of several series of the writer's experiments. 



TABLE I. 



EFFECTS OF TEMPERATURE. 



It was peculiar that high and low temperatures had the same 

 reversing effect on the larvae, although cold was slower and less 

 effective. Loeb 1 showed in Polygordius larvae a phenomenon 

 similar to this. 



2. Effects of Hyper tonic and Hypotonic Sea-water. 



(a) Effect of Hypertonic Sea-water. R. S. Lillie 2 and Mast 3 

 observed that hypertonic and hypotonic sea-water produced the 

 reversal of the normal heliotropism in Arenicola larvae. The 

 writer tested the effect of hypertonic sea-water by mixing 15 c.c 

 of one mol NaCl solution and 35 c.c. of natural sea-water at 

 room temperature, 22 C. He found that about 20 per cent, 

 of larvae became negative. He did not, however, succeed 

 in producing a reversal in this medium by raising or lowering 

 temperature, i. e., 32 C. or 12 C. The larvae in this mixture 

 were very sluggish at these temperatures. 



In the mixture of 0.85 c.c. of m-KCl solution and 50 c.c. of 



1 Loeb, J., loc. oil. 

 - Lillie, R. S., loc. cit. 

 3 Mast, S. O., loc. cit. 



