Inheritance of Acquired Characters 237 



the egg, or to the immaturity or impotence of some of the 

 male germ-cells, and not to the need of more than one to 

 accomplish the true fertilization. 



Darwin's idea that the small number of gemmules in the 

 unfertilized egg may account for the lack of power of such 

 eggs to develop until they are fertilized, has been shown to 

 be incorrect by recent results in experimental embryology. 

 We now know that many different kinds of stimuli have the 

 power to start the development of the egg. Moreover, we 

 also know that if a single spermatozoon is supplied with a 

 piece of egg-protoplasm without a nucleus, it suffices to cause 

 this piece of protoplasm to develop. 



In the case of regeneration, which Darwin also tries to 

 explain on the pangenesis hypothesis, we find that there is 

 no need at all for an hypothesis of this sort ; and there are a 

 number of facts in connection with regeneration that are not 

 in harmony with the hypothesis. For instance, when a part is 

 cut off, the same part is regenerated ; but under these circum- 

 stances it cannot be imagined that the part removed supplies 

 the gemmules for the new part. Darwin tries to meet this 

 objection by the assumption that every part of the body con- 

 tains gemmules from every other part. But it has been 

 shown that if a limb of the newt is completely extirpated, a 

 new limb does not regenerate ; and there is no reason why it 

 should not do so on Darwin's assumption that germs of the 

 limb exist throughout the body. 



The best-authenticated cases of the influence of the male 

 on the tissues of the female are those in plants, where one 

 species, or variety, is fertilized by another. Thus, if the 

 orange is fertilized by the pollen of the lemon, the fruit may 

 have the color and flavor of the lemon. Now the fruit is a 

 product of the tissues of the ovary of the female, and not a 

 part of the seedling that develops in the fruit from the cross- 

 fertilized egg-cell. Analogous cases are recorded for the 

 bean, whose pods may have their color influenced by fertil- 



