296 HEREDITY AND ENVIRONMENT 



Plate calls all such cases "Pseudo-heredity," 

 because they have nothing to do with inheri- 

 tance units, or with special qualities of the 

 germ plasm, but are dependent upon the cyto- 

 plasm. We may agree with Plate that no 

 character is inherited unless its differential 

 cause is found in the organization of the germ 

 cells, but it is certainly an indefensible defini- 

 tion of heredity which limits it to inheritance 

 units transmitted only through the nucleus. 



Other forms of transmission are known in 

 which substances are carried over from one 

 generation to the next through the egg, but 

 they are probably not cases of true inheritance. 

 Among these are the occasional transmission 

 of immunity through the mother but never 

 through the father, the carrying over of par- 

 ticular chemical substances such as fat dyes 

 through the egg but not through the sperm, 

 and the transport of symbiotic or parasitic or- 

 ganisms, such as algae, bacteria, etc., through 

 the female sex cell but not through the male 

 cell. These substances or micro-organisms are 

 to be regarded as inclusions in the egg rather 

 than as any permanent part of the germinal 

 organization; consequently they are not in- 

 herited in the strict sense of that term. 



