The Infuence of External Factors ofi Developiuent 1 91 



solution of NaCl in sea-water and they continued to develop in an 

 apparently normal fashion but with their yolks shrunken. Loeb 

 ('94) had found that embryos three or four days old might be placed 

 into a 2/2 per cent sea-water solution of NaCl and continue nor- 

 mal development. None of these embryos, however, will hatch. 



In several of the NaCl solutions I found embryos that lacked 

 all skin pigmentation thus appearing almost white, these were not 

 true albinos, however, since their eyes showed pigment. Such 

 pale embryos hatched when returned to sea-water. 



After a consideration of the foregoing results one must admit, it 

 seems to me, as probable that some of the elements exert a specific 

 stimulus on the fish embryo and cause it to develop in a character- 

 istic manner. LiCI, KCl, MnCU and MgCU seem to induce 

 rather constant and definite effects or types of embryos. The 

 form of the embryo seems to be influenced by external factors in 

 development as well as by internal ones; in other words, the chemi- 

 cal environment of an egg is important in determining the final 

 resultant of the factors in inheritance. 



It may be suggested as a probability that every element that 

 forms a chemical union with the germ substance produces on the 

 developing egg through its action definite anatomical and physio- 

 logical eff'ects, which of course will vary in different kinds of eggs. 

 Thus since the normal form of an animal may be altered in a defi- 

 nite way by certain chemical actions of the elements, we may 

 assume that the specific nature of any animal is a product of the 

 chemical composition of the egg cell from which it sprang. 



THE ACTION OF MIXTURES OF SALTS IN SOLUTION: THE CHEMICAL 

 VERSUS THE OSMOTIC EFFECTS 



The following experiments were conducted in order to deter- 

 mine whether or not by increasing the osmotic pressure of the solu- 

 tion through the addition of a chemically indifferent substance, such 

 as sugar, the chemical action of salts might be augmented. In 

 other words, will eggs become more susceptible to the chemical 

 action of a weak salt solution if the osmotic pressure of this solution 

 be increased ? Morgan ('06) has performed similar experiments 



