312 The Influence of Environment 



heart will continue to beat normally and the em- 

 bryo will continue to develop for three days or more, 

 because the calcium prevents the NaCl from entering 

 into the egg. 1 For if we put a newly hatched embryo 

 into 50 c.c. 3 m NaCl+i c.c. 10/8 m CaCl 2 it will die 

 almost instantly; hence the membrane must have 

 acted for three or more days as a shield which pre- 

 vented the NaCl from diffusing into the egg in the 

 presence of CaCl 2 . 



The same experiments cannot be demonstrated in 

 the sea-urchin egg, first, because it can live neither in 

 distilled water nor in very dilute nor very concentrated 

 solutions; and second, because it is not separated as is 

 the germ of the Fundulus egg from the surrounding 

 solution by a membrane which is under proper condi- 

 tions practically impermeable for water and salts. 



Nevertheless it can be shown that the results at 

 which we arrived in our experiments on Fundulus 

 are of a general application. Osterhout 2 has shown 

 that plants which grow in the soil or in fresh water 

 are readily killed by a pure NaCl solution of a certain 

 concentration, while they can resist the same concen- 

 tration of NaCl if some CaCl 2 is added. Wo. Ostwald 3 

 has shown the same for a species of Daphnia. We, 

 therefore, come to the conclusion that the injurious 



1 Loeb, J., Biochem. Ztschr., 1912, xlvii., 127. 



3 Osterhout, W. J. V., Bot. Gazette, 1906, xlii., 127; 1907, xliv., 257; 

 Jour. BioL, Chem., 1906, i., 363. 



? Ostwald, Wo., Arch.f. d. ges. Physiol., 1905, cvi., 568. 



