REVERSIBILITY OF HELIOTROPISM OF ARENICOLA LARV/E. 163 



obtained by the writer did not agree well with those of Loeb, as 

 in the case of fatty acids. For instance, in 0.0036 m. HC1 

 solution made with sea-water, about 80 per cent, of the larvae 

 became negative and in similar solutions of H2SO4 about 95 per 

 cent, became negative 15 minutes after the treatment at 21 C. 

 The negative larvae, however, showed marked abnormality. 

 This was the only case of failure, so far as the writer found, in 

 the parallelism between the effects of chemical substances in 

 producing artificial parthenogenesis in sea-urchin eggs and in 

 reversing the positive heliotropism of Arenicola larvae. 



The writer also found at the Marine Biological Laboratory of 

 the Kyushu Imperial University, Fukuoka, Japan, in the summer 

 of 1916, that a marine crustacean, Astracoda Cypridina (hilgen- 

 dorfi) which was strongly negative to light, could be made positive 

 by HC1 or H 2 SO 4 solution. Quantitative data were not ob- 

 tained owing to illness. 



That acids, organic and inorganic, are able to penetrate the 

 living cell, is proved by Harvey. 3 It seems possible therefore 

 that both HC1 and H 2 SO 4 penetrated into Arenicola larvae. 



13. Effects of Strong and Weak Bases. 



Loeb discovered that "the weak base NH 4 OH is much more 

 efficient for the causation of artificial parthenogenesis in Arbacia 

 eggs than the strong bases, NaOH, KOH and tetraethylam- 

 monium hydroxide," 1 N(C 2 H 5 ) 4 OH. The writer found that this 

 was also the case in the production of negative heliotropism in 

 Arenicola larvae. The essential results of his experiments may 

 be summarized thus: in the appropriate concentration of NH 4 OH, 

 about 70 per cent, of the larvae became negative after about 20 

 minutes exposure to the solution at 21 C., whereas in equivalent 

 solutions of NaOH, KOH, or N(C 2 H 5 ) 4 OH, only about 10 or 15 

 per cent, of the larvae became negative after an exposure of about 

 60 minutes at this temperature. This difference may be ex- 

 plained by the fact that the living cell is permeable to ammonium 

 hydroxide but impermeable to sodium hydroxide and other 

 strong bases, as experiments of Bethe 2 and Warburg 3 have 



1 Harvey, E. Newton, Science, N. S., Vol. 39, p. 947- I9M- 



2 Loeb, Jacques, Jour. Ex. Zoo/., Vol. 13, p. 577, 1912. 



3 Bethe, Albrecht, Pfliiger's Arch., Bd. 127, S. 219, 1909. 



4 Warburg, Otto, Zeits. physiol. Chem., Bd. 66, S. 305, 1910. 



