Nabours : Promises and Limitations of Eueenics 



279 



thing as the heritage without environ- 

 ment or the environment without the 

 heritage — no possibility of the consid- 

 eration of nature w^ithout nurture, or, 

 nurture without nature. Ihe factors 

 of each are inextricably involved w^ith 

 the other. It is a big step forward 

 that all can agree on this point, as I 

 believe we do, but even so. we have 

 onlv arrived at the stage where dis- 

 criminate consideration is ])0ssible. 



Are Acquired Characters Inherited? 



We are impelled thus to inquire 

 whether changes in the environment, 

 or nurture, will change the nature that 

 has been inherited in such manner 

 that the changes that may be accom- 

 plished can be transmitted to the off- 

 spring. 



Among the biologists I am sure it 

 is well known that this question of 

 the inheritance of acquired characters, 

 or the induced mutability of the ger- 

 minal substance, is to the front and 

 is probably as lively a subject of dis- 

 cussion today as it ever has been in 

 the past. Let us examine this ques- 

 tion as well as may be possible in the 

 time at our disposal. No detailed 

 presentation of the data is intended 

 now ; only references may be made to 

 some of the more prominenz experi- 

 ments. 



In the famous ex])eriments of 

 Brown-Sequard, epilepsy and other 

 characters were induced in guinea pigs 

 by severing the spinal cord, or sciatic 

 nerves. These acquired characters ap- 

 parently were inherited by the off- 

 spring, but I believe geneticists now 

 recognize that this claim has been re- 

 futed several times. I know no in- 

 vestigator who now attributes, except 

 historically, the slightest importance 

 to them. 



Tower's experiments with potato 

 beetles were popularly widely hailed 

 as giving convincing proof of the pos- 

 sibility of the permanent modification 

 of the substance bearing the factors 

 of the heritage by the impingment of 

 the environment, but critical examina- 



tion of his data leaves much to be de- 

 sired. 1 believe it is the consensus of 

 judgment, and without disparagement 

 of his brilliant achievements, that an 

 open mind should be maintained con- 

 cerning the interpretations which 

 ought to be given to his results. 



Kammerer, an Austrian biologist, 

 has |)ublishe(l accounts of experiments 

 on the inheritance of induced char- 

 acters in certain amphibia. In the one 

 case a frog, Alytcs ohstcfricaiis, is 

 found in nature to have departed from 

 the usual habits of frogs to the extent 

 that the eggs are laid and fertilized 

 while the pair are on the land. After- 

 ward, the male, on whose hind legs 

 the fertilized eggs are retained, seeks 

 water where hatching takes place and 

 a very short tadpole stage is passed. 

 Furthermore, in nature, the male of 

 Alyfcs does not have pads, or swell- 

 ings, on his thumbs which are com- 

 mon on the thumbs of other frogs 

 that mate in the water where the pads 

 are thought to be helpful in holding 

 to the bodies of the females. Briefly 

 stated, Kammerer maintains that he 

 has, by forcing these frogs to mate in 

 the water through a few generations, 

 caused theiu and their offspring to re- 

 tain the habit of mating in the water, 

 even when restored to conditions fa- 

 vorable for mating on land, and that 

 the tadpole stage has been greatly 

 lengthened. But of probably greater 

 significance, the male has developed 

 the pads, or swellings, on the thumbs 

 which enable him to hold the females 

 better while mating in the water. All 

 this is thought to be a restoration, and 

 causing to be inherited, of characters 

 which these frogs are supposed to 

 have lost, presumably by use and dis- 

 use, in the same way as they have 

 now been restored. 



Kammerer claims also that he has 

 induced heritable color changes in 

 salamanders by maintaining them on 

 differently colored soils. 



Professor Bateson has assailed 

 Kammerer's work on a number of 

 points which are too extensive to be 



