Phenomena of Inheritance 115 



delian in the previous generation, this also being a case of pre- 

 inheritance. 



It has been found by Correns, Baur, and Shull that the leaf 

 colors of certain plants are not inherited in Mendelian fash- 

 ion, but the chromoplasts, which produce the chromatophores 

 (chloroplasts), are transmitted from one generation to the next 

 in the cytoplasm of the egg cell and only rarely through the 

 male sex cell. If chromoplasts are integral parts of a plant 

 and undergo differentiation or development this may be a case of 

 pre-inheritance ; if they are symbiotic organisms it is an instance 

 of the inclusion of foreign bodies in the cytoplasm and not in- 

 heritance at all. 



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 particular 

 chemical substances such as fat dyes through the egg but not 

 through the sperm, and the transport of symbiotic or parasitic 

 organisms, such as algae, bacteria, etc., through the female sex 

 cell but not through the male cell. These substances or micro- 



itli 



iw 

 % 



B A 



FIG. 38. X-RAY PICTURE, A OF A NORMAL, B OF A SHORT-FINGERED 

 (brachydactyl) hand. (From Bateson.) 



