The Inheritance of Acquired Characters 61 



previous sire to be seen in the later offspring. The experiments 

 were made with pedigree stock, and the results are convincing, 

 and indicate that the belief in an influence of this kind is another 

 breeders' myth. Minot has also obtained negative evidence 

 with guinea pigs, and I have obtained similar negative evidence 

 with mice. 



Xenia 



It has been claimed that in plants the influence of the pollen 

 is sometimes shown in those parts of the fruit or of the seed that 

 are derived from the mother plant. 1 The flower of the orange, 

 fertilized accidentally by pollen from the lemon, is said some- 

 times to produce fruit that may show a stripe in the peel like 

 that of the lemon, although the peel is a product of the tissues 

 of the mother plant. Similar cases have been recorded for the 

 seed-color, and even for the pods of peas. The most familiar 

 case is that of the color of the grains of maize. 



In recent years it has been shown that some, at least, of these 

 cases can be explained as the result of a process of double fer- 

 tilization. It has been found that there enters the embryo sac 

 not only the sperm-nucleus, that unites with the ovum, but 

 another nucleus that fuses with the "polar" nucleus or nuclei. 

 The latter combination gives rise to the endosperm, which is 

 therefore hybrid in origin, and may show the influence of the 

 sperm nucleus if this contains the dominant character. 



In regard to the other cases, where the color is not in the endo- 

 sperm, the results cannot be ascribed to the sperm nucleus. 

 Giltay, who has made some experiments to test this point in 

 peas, found no instances where the color of the pods could 

 be assigned to the influence of pollen plant. 2 



Theories of Transmission of Somatic Influences 



The only theory of any prominence that pretends to indicate 

 how changes in the somatic cells may affect the germ-cells is 



1 From the nature of the case the process could not be expected to occur in 

 animals. 



2 See Davis, B. M., American Naturalist, XXXIX, August, 1905. 



