m. 643] SEROLOGICAL PHENOMENA 



133 



repeatedly. And since satisfactory adjustment to the 

 new conditions must mean not only one. but many favor- 

 able and interrelated variations, it seems almost incredible 

 that the adaptedness characteristic of the organisms in 

 question was attained merely through the operation of 

 natural selection generation after generation on as- 

 semblages of purely accidental mutations. Palaeontolo- 

 gists tell us that times of marked evolutionary change 

 have coincided with periods of great geological change- 

 extremes of temperature, moisture or drought, or fairly 

 rapid fluctuation between such extremes. And while such 

 conditions would undoubtedly favor a maximal opera- 

 tion of natural selection, it is well to remember also that 

 the severe strains of somatic adjustment forced upon or- 

 ganisms existing at the time would doubtless result in a 

 maximal sweep of serological influences through the 

 sorely pressed body. 



Although I have emphasized one side of the problem of 

 variation, I am not unmindful of the remarkable stability 

 of the germinal protoplasm as we see it expressed in or- 

 ganisms to-day. It is obvious that not every minor or 

 temporary alteration in somatic mechanism is reflected 

 in the germ to any measurable extent. Since probably no 

 two living things of any kind are equally susceptible to 

 external influence, individual germ-cells doubtless vary 

 in susceptibility, possibly even the same germ-cell would 

 respond differently at different stages of maturity. It is 

 not unreasonable to believe, moreover, that only a few 

 out of many germ-cells might be sufficiently affected to 

 make a perceptible difference. I have already expressed 

 the opinion" elsewhere that ''no one to-day, qualified by 

 his knowledge of embryology and genetics to the right of 

 an opinion, would, I think, deny that the new organism 

 is in the main the expression of what was in the germ- 

 line, rather than of what it got directly from the body 

 . . . ." But we know that the germ does change from 

 time to time and it seems to my mind not illogical to sup- 

 pose that at least some of the changes are specifically re- 

 lated to changes in the soma. 



7 Am. Nat., LV, Mar.-Apr., 1921. 



