54 Heredity. 



iited certain functions to the ovum and certain others 

 to the male cell does not, of course, prove that there is 

 no difference in the functions of these elements ; but in 

 modern times we actually find that thinkers have gone 

 to this opposite extremity of the subject, and have 

 either tacitly implied or directly accepted the view 

 that the two sexual elements play similar parts in 

 heredity. 



Neither Ilaeckel's hypothesis nor Jilger's recognizes 

 any difference in their functions, Avhile Jager seems to 

 believe, and Darwin explicitly states, that their shares in 

 hereditary transmission are alike. 



Many facts indicate that this view is, to say the least, 

 Tery improbable, and I will give, biiefiy, a statement of 

 some of the arguments against it, and Avill then devote 

 a little space to a discussion of the reasons Avhich have 

 been given by Darwin and others for accepting it. 



The structural difference between the ovum and the 

 male cell is one of the most widespread and fundamcntnl 

 characteristics of organic beings, and it is found in all 

 except the very lowest animals and plants. It is, to say 

 the least, very improbable that a structural difference so 

 fundamental and so nearly universal should have no 

 functional significance, and the fact that in many marine 

 animals, when the ripe unfertilized ova are throAvn out 

 into the ocean, like the male fluid, to be swept away by 

 the tide, the sexual elements differ in the same way that 

 they do in animals whose eggs are fertilized inside the 

 body of the female, forbids us to believe that the differ- 

 ence depends simply upon the fact that the male cell 

 must make its way to the ovum. 



Many of the secondary characteristics of the ovum, 

 such as its great size in birds and reptiles, and the pres- 

 ence in it of food-material in so many animals, are no 



