THE CELLULAR BASIS 183 



istic polarity, symmetry and pattern of the 

 cytoplasm of the egg either before or immedi- 

 ately after fertilization. In all of these phyla 

 eggs may develop without fertilization, either 

 by natural or by artificial parthenogenesis, 

 and in such cases the characteristic polarity, 

 symmetry and pattern of the adult are found 

 in the cytoplasm of the egg just as if the lat- 

 ter had been fertilized. The conclusion seems 

 to be justified that these earliest and most 

 fundamental differentiations which distin- 

 guished the eggs of various phyla are not de- 

 pendent upon the entering spermatozoon. 



All of these correspondences between the 

 polarity, symmetry and pattern of the egg 

 and of the developed animal are found in the 

 cytoplasm. No doubt the differentiations of 

 cytoplasm of the egg as well as the peculiar 

 form and structure of the spermatozoon have 

 arisen during the genesis of these cells under 

 the influence of paternal and maternal chro- 

 mosomes contained within their nuclei, just as 

 in the differentiation of anjr tissue cell; but in 

 the case of the spermatozoon these cytoplasmic 

 differentiations are lost when it enters the egg, 



