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THE AMERICAN NATURALIST [Vol. LVI 



could be passed down through the male line alone it is 

 evident that it is based on changes in the germ-cells. 



In later experiments we obtained similarly defective 

 young by injecting rabbit-lens into pregnant rabbits, al- 

 though we secured this result only after repeated trials 

 and in the young of but one female. Our belief is that 

 the cytolytic serum not only attacked the newly forming 

 fetal lens, but also its representatives in some of the germ- 

 cells of the fetus. This implies, of course, that there is 

 a sufficient thread of chemical identity between the two 

 to render them both susceptible to the same specific in- 

 fluence. 



For such serumal effects to be of significance in evolu- 

 tion, however, the antibody or other factor operative on 

 a given tissue-protein would have to be one that could 

 arise directly in the organism itself. But since it is 

 known that animals will develop anaphylaxis against tis- 

 sues of their own species, and that a rabbit can be made 

 to build spermatotoxins against its own spermatozoa, it 

 is reasonable to suppose that if an animal's own tissues 

 became displaced, injured or otherwise modified, they 

 might cause the production of antibodies. And these, 

 carried by the circulating fluids of the body into the 

 gonads, would have opportunity to influence such protein- 

 complexes there as were similar to those in the tissues 

 which served as antigens. Nor need the germinal and 

 somatic elements in question be identical in constitution, 

 for it is known that while an antibody against a particular 

 tissue shows its highest degree of specificity only against 

 that tissue, nevertheless, it will also react in some degree 

 with other tissues of the same individual. This phenom- 

 enon, termed species-specificity, clearly indicates that 

 there is a broad common basis of chemical identity under- 

 lying all the tissues of an organism. It is not unreason- 

 able, then, to believe that there is sufficient chemical iden- 

 tity between the proteins of tissue cells and the related 

 proteins of the germ for both to be influenced by the 

 same agents. 



To construct a working hypothesis upon the possibilities 



