MEANS AND METHODS OF EVOLUTIONARY CHANGE 345 



the experiment was terminated by a fatal epidemic before the inheritance 

 of the defect by later generations could be proved. But the defects were 

 similar to those whose inheritance had been proved in previous experi- 

 ments. Here, then, was an instance in which an external agent (the experi- 

 menter's needle) produced a change in the body (destruction of the lens) 

 which was then apparently transferred to the male rabbit's germ cells, pre- 

 sumably through the agency of antibodies. Taken at its face value, was this 

 an instance of inheritance of acquired characters in the Lamarckian 

 sense? Perhaps the antibodies had induced the formation of mutations in 

 the genes controlling eye formation, as mentioned previously (p. 339). If 

 so, would this condition constitute inheritance of acquired characters? If 

 antibody formation resulted from a change in the body, and then the anti- 

 bodies induced changes in the genes concerned with the characteristic in 

 question, we should have something which to all intents and purposes 

 would be inheritance of acquired characters. But the foregoing statement 

 begins with "If"; indubitable proof that such a sequence of events can 

 actually occur is lacking, though its possibility is suggested by these pio- 

 neer experiments of Guyer and Smith, supplemented by investigations 

 of others on antibody induction of mutations. 



Critics of the experimentation of Guyer and Smith have not been lack- 

 ing. Other investigators have repeated the experiments, usually with some 

 variations, and have not obtained the same results. One objection raised 

 is that since rabbits sometimes carry recessive genes for eye defects, 

 perhaps the stock used by Guyer and Smith was thus contaminated, the 

 defects coming to light just at the time of experimentation but not because 

 of the experimental procedures. Guyer has replied in rebuttal that control 

 animals from the same stocks as the experimental animals did not show 

 eye defects. He recorded seeing one rabbit with defective eyes among a 

 total of 2000 individuals. Nevertheless, future experimenters must employ 

 highly inbred stocks so that all recessive genes will be brought together in 

 homozygous state and thus betray their presence by producing visible ef- 

 fects. 



What is our verdict concerning the efficacy of inheritance of acquired 

 characters as a means of producing new characteristics? Evidently we 

 must bring in the Scotch verdict of "not proven." But it will be well to 

 leave our minds open to the possibility that, in the particular circum- 

 stances in which antibodies may serve as intermediaries between change- 

 in-body and the germ plasm, something amounting to inheritance of ac- 

 quired characters may yet be demonstrated. If later investigation proves 

 the occurrence of mutation directed by antibodies, mutations and acquired 



