6O INTRODUCTION. 



cytoplasmic band and blepharoplast, or cilia-bearer, enter the egg, 

 yet their function seems to be of secondary importance as compared 

 with that of the nucleus. Again in the higher seed-bearing plants, 

 the generative nuclei are accompanied by only a small portion of cyto- 

 plasm, which cannot be recognized in the embryo-sac, and it seems 

 reasonable that it is merely absorbed as so much food. However, 

 when we remember that in all cases of fecundation at least some 

 cytoplasm accompanies the male nucleus into the egg, there is good 

 ground for the belief that the cytoplasm plays some important rdle, 

 but whether that be anything more than to assist in restoring the 

 power of growth and division must at present remain a question. 



The behavior of the sexual nuclei during the process of fecundation 

 and the wonderful phenomena of karyokinesis point to the conclusion 

 that the nucleus is the bearer of hereditary characters, and that the 

 blending of these characters in the offspring are largely the result of 

 the fusion of the sexual nuclei. The nuclear fusion is also the basis 

 of all hereditary variation. 



