CHAPTER XIII 



HEREDITY AND VARIATION 



Fertilisation Parthenogenesis Heredity Particulate 

 and Mnemic Theories Variation. 



THE ovum from which the adult form develops 

 is in the enormous majority of cases the result 

 of the fusion of elements derived from two 

 parents, male and female. Thus in the vege- 

 table kingdom the pollen granules, shed from 

 the anthers of the stamens of the male plant 

 or portion of the plant, are conveyed by in- 

 sects or by the wind or otherwise to the stigma 

 of the female plant or portion of the plant. 

 Uniting with the ovules in that portion they 

 form the future seeds. In the animal kingdom 

 the male spermatozoon unites with the ovum 

 from the female, which it enters, fertilises and 

 as a result forms the commencement of a new 

 being. 



There are, however, cases in which develop- 

 ment takes place without such union. These 

 cases come under the category of what is known Partheno- 

 as partho genesis and, as some importance has S enesis 

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