28 Outline of Genetics 



identity, probably protein homology, between the mature sub- 

 stance of a tissue and its correlative in the germ," and that "basi- 

 cally, inheritance is mainly a question of the perpetuation of spe- 

 cific protein-complexes, and development the result of differential 

 reactions of these same fundamental constituents under different 



conditions of environment Is it unreasonable to suppose that 



if changes come to pass which affect certain constituents of tissue 

 cells, this influence, if borne in the circulating fluids of the body, 

 could also affect the hom^ologous constituents of the germ cells?" 



The same result has been obtained by the direct injection of 

 lens-extract into the blood stream of the rabbits themselves. It 

 is perhaps surprising that rabbits will manufacture antibodies 

 for one of their own tissues. It is evident that they do, however, 

 and this brings us a distinct step closer to something that m'ght 

 occur under natural conditions. If degenerating eyes may them- 

 selves originate antibodies which in turn affect the germ cells, the 

 cardinal principle of Lamarck's theory of evolution through 

 inheritance of acquired characters must be conceded. 



The fact that the eyes of the pregnant mothers were in no case 

 themselves affected does not necessarily recommend the assumption 

 of "susceptibility" only in the embryonic state, but is doubtless 

 due merely to the fact that there is a relatively much greater blood 

 supply to the lens of embryo rabbits than those of adults. 



The experiments of Griffith and Detlefsen, final results of 

 which have not yet been published, promise to provide an equally 

 good demonstration of inheritance of acquired characters in mam- 

 mals (see Science 56:676-678. 1922). 



A few examples of the supposed inheritance of the 

 ''effects of environment" in plants should be considered. 

 Zedebaur found that Capsella, which in the course of 

 many years had gradually crept along the roadside up 

 into an alpine habitat and there acquired alpine char- 

 acters, retained these characters when transplanted to 

 the lowlands. This has been accepted by some as an 

 authentic instance of inheritance of acquired characters; 

 but it is possible that this conquest of an alpine habitat 



