HEREDITY 



macro-gamete) in all animals is non-motile and 

 contains a relatively large amount of reserve- 

 food material for the maintenance of the de- 

 veloping embryo. This reserve-food material 

 it is the function of the mother to supply. In 

 the case of some animals, for example flat- 

 worms and moUusks, the food-supply of the 

 embryo is not stored in the egg-cell itself, but 

 in other cells associated with it, and which 

 break down and supply nourishment to the 

 developing embryo derived from the fertilized 

 egg. Again, as in the mammals, the embryo 

 may derive its nourishment largely from the 

 maternal tissues, the embryo remaining like a 

 parasite within the maternal body during its 

 growth, feeding by absorption. But in all cases 

 alike the mother supplies the larger gamete 

 and the food-material necessary to carry the 

 zygote through its embryonic stages. The 

 father, on the other hand, furnishes the bare 

 hereditary equipment of a gamete, with the 

 motor apparatus necessary to bring it into 

 contact with the egg-cell, but without food for 

 the developing embryo produced by fertiliza- 

 tion. The gamete furnished by the father is 



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