CHAPTER VI 

 THE VISIBLE BASIS OF HEREDITY 



As we have seen in a preceding chapter, 

 when the eggs of the frog are shed into the 

 water by the female, the male at the same time 

 discharges the sperm on to them. The pair of 

 frogs then pay no more attention to their 

 eggs. Such fertilized eggs have no connection 

 with the bodies of their parents, so that what- 

 ever hereditary characters are displayed by 

 the young frogs must evidently be trans- 

 mitted entirely through the eggs and sperm. 

 A similar situation obtains among many of 

 the lower plants and a majority of animals; 

 the egg develops entirely dissociated from the 

 parent. While in the higher animals the egg, 

 during its development, is held in one of the 

 reproductive organs of the mother (the womb 

 or uterus), the connection of the growing 

 embryo with the parent is not as close as at 

 first appears; no blood flows from the parent 



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