EVOLUTION 9S9 



separated from the parent. A similar result in mammals might be 

 readily confused with inheritance. 



IV. There is an increasing body of facts pointing to the conclusion 

 that changes in nurture may serve as variational stimuli; that is 

 to say, that they may affect the germ-cells through the parent, so 

 that a variation occurs in the offspring. Thus, Tower subjected 

 potato-beetles, at a certain stage of their development, to unusual 

 conditions of temperature and humidity. The body of the beetles 

 exhibited no modification, and that was not to be expected. But in 

 a number of cases the offspring of these beetles showed remarkable 

 changes in colour and markings, and even in minute details of 

 structure. And there was no reversion to the parental condition. 

 Tower's experiments require confirmation and extension, but it 

 looks as if a peculiarity in the environment might serve as a 

 liberating stimulus to germinal variability. 



Attention may also be directed to the probability that much 

 may depend upon the nurtural reception that a natural variation 

 meets with. Unless the nurture evolves progressively along with the 

 nature (and in mankind especially), many new departures may be 

 blocked at the outset ; many promising variations may be bom only 

 to die, or die too soon. Does not human biography give only too 

 many instances of this ? 



On no account whatsoever are we to countenance, if we can help 

 it, spoiling good stock by bad; but it is a dubious inference that the 

 bad is hopeless. It may often be that it is not so bad as it looks. In 

 her interesting study. Environment and Efficiency (Longmans, 1912), 

 Miss Mary Horner Thomson tells of her study of 265 children, 

 mostly of "the lowest class" (Class A, fourth below the poverty 

 level!), who had been sent to institutions and trained. She found that 

 192 (72 per cent.) turned out well; that 44 (16 per cent.) were 

 doubtful; and that only 29 (less than 11 per cent.) were unsatisfac- 

 tory, and of these 13 were defectives. These figures, which other good 

 orphanages justify, but which should be widely collected and 

 compared, afford some evidence of the controllability of life. 



IN CONCLUSION.— Illustrations have been given of a number 

 of facts : that nurture is important as a condition of normal develop- 

 ment; that on its liberating stimuli the degree of development in 

 part depends; that even a slight change in nurture may mean a 

 great deal; that in mammals especially it is not always easy to 

 distinguish what is in the strict sense inherited from what is due to 

 ante-natal nurture ; that nurtural effects, though not transmissible, 

 may be in several ways of indirect racial importance. It has also 

 been pointed out that there are some facts suggesting the theory 

 that peculiarities of nurture may act on the germ-cells as variational 

 stimuli — tending to the emergence of the new. 



