THE CELLULAR BASIS 159 



vironment they must be due to differences in 

 the germ cells concerned. 



On the other hand different environmental 

 conditions may be associated with similar de- 

 velopmental results. Loeb and others have 

 found that artificial parthenogenesis may be 

 induced by a great variety of environmental 

 stimuli, viz., by salt solutions, by acids and 

 alkalis, by fatty acids and fat solvents, by 

 alkaloids and cyanides, by blood serum and 

 sperm extract, by heat and cold, by agitation 

 and electric current. There is certainly noth- 

 ing specific in these different stimuli. Simi- 

 larly Stockard has discovered that cyclopia, 

 or one-eyed monsters, may be produced by 

 magnesium salts, alcohol, chloretone, chloro- 

 form, and ether, and to this list McClendon has 

 added various other salts and anaesthetics. In 

 all such cases it is evident that the specific re- 

 sults of such treatment are due to a specific 

 organization of the germ rather than to specific 

 stimuli. 



Why does one egg give rise to a chicken 

 and another to a duck, or a fish, or a frog? 

 Why does one egg give rise to a black guinea- 



