EwAUT — Variation : Germinal and Environmental. 357 



II. — Environmental changes from the end of development to the end of the 

 reproductive period, including changes in the germ-cells during 

 their growth and maturation. 



(1). Experiments bearing on the question of the inheritance of acquired characters. 



Every plant and animal has a certain amount of plasticity, just as every 

 species has certain potentialities. 



In virtue of this plasticity both plants and animals, by responding to external 

 stimuli, are able, during their lifetime, to adapt themselves, within certain 

 limits, to their environment. By treating individual plants and animals of the 

 same variety differently — no matter how intimately related — surprisingly diverse 

 results (difference in size, in the time maturity is reached, fertility, &c.) are 

 sometimes obtained, nurture during at least the individual life having, in many 

 cases, a wonderful power over nature. Can any of the results of nurture (acquired, 

 it may be, at the expense of much time and energy), changes in habit, or in 

 structure, in size or colour, in mind or muscle, be handed on even in a modified 

 way to the offspring ? In other words, is it possible, in some incomprehensible 

 way, to engraft on the germ-plasm specific somatic changes acquired during the 

 life of the individual, i.e. to transmute definite envii'onmental somatic variations 

 into germinal variations ? To this still burning question many, following Darwin, 

 would give an affirmative answer, while Weismann and his followers would as 

 unhesitatingly reply in the negative. 



Darwin, Spencer, and many others — doubting, apparently, the sufficiency of 

 germinal variations, and failing, jjerhaps, to realize sufficiently the influence of 

 the environment on the germ-plasm — imported into the new evolution hypothesis 

 some of the old hypotheses generally associated wdth the name of Lamarck. 

 Hence, until Weismann adversely criticised the want of confidence alike of 

 prophets and followers in the new doctrines, and insisted on the all- sufficiency 

 of congenital (germinal) variation, it was commonly believed that all sorts of 

 peculiar mental and physical traits — normal and abnormal — acquired for the 

 first time by the parents, could be handed on practically unchanged to their 

 offspring. 



I have not yet met with any evidence in support of the belief that specific 

 acquired somatic variations are hereditary. On the contrary, many of my 

 results indicate that the handing on, even in a highly modified form of definite 

 (non-latent) traits acquired during the lifetime, is extremely improbable. 



Some of these results may be worth mentioning. Hitherto tails and horns 



