Inheritance Materials of Germ-Cells 73 



actually before us in the recent history of biology. 



Viewing heredity as being definitively a kind of organic 

 transformation transformation, that is, in accordance with 

 a pre-existing or ancestral pattern more than it is a kind 

 of continuity it becomes obvious that even were the dem- 

 onstration to become complete that the chromosomes are 

 the only portions of the germ-cells * essential to fertiliza- 

 tion, they still would not be proved bearers of heredity in 

 such sense as the germ-plasm theory holds them to be. They 

 would not because the problem of the transformations 

 which constitute ontogeny would still be untouched. The 

 theory would be established only when the demonstration 

 should be produced that the chromosomes cause immedi- 

 ately all the particular ontogenic transformations known 

 to be hereditary. All that would be proved about heredity 

 by demonstration that the chromosomes alone participate 

 in fertilization would be that the chromosomes alone con- 

 stitute the first ontogenic stage of the hereditary parts of 

 the particular organism to which the fertilized egg gives 

 rise. 



The Probability That Inheritance Material Becomes Such 

 In Each Ontogeny 



But because thus far failure has attended all efforts to 

 get knowledge of how hereditary substance is produced, 

 are we obliged to own that we know nothing at all, even 

 inferentially, about its production? And is the search for 

 such knowledge to be given up as hopeless? My answer is 

 an energetic negative to both these questions. In the first 

 place, there is much evidence to support the hypothesis, 

 very general to be sure but yet by no means devoid of use- 

 fulness, that hereditary substance becomes such in some 



* The utter unwarrantableness of the common assumption that as 

 regards the male germ-cell such a demonstration is "practically com- 

 plete" will be noticed presently. 



