244 Biology in America 



changes in its environment, either internal * or external. The 

 former metliod is metaphysical and unscientific; the latter, 

 while beset by many difficulties, is the only one of promise. 



What then has been done to discover the influence of en- 

 viroiunent upon variability? In a previous chapter we have 

 briefly surveyed tlie influence of environment upon individ- 

 ual development, and have seen that this influence is often 

 of a profound character. But is such influence lasting, does 

 it through heredity control future as well as present gen- 

 erations? And this brings us face to face with one of the 

 greatest stumbling blocks in biology ; namely, the inheritance 

 of acquired characters. 



In the first place what is the meaning of the term? V{e 

 owe the theory to the great French naturalist Lamarck, one 

 of those lonely and pathetic figures who look down upon the 

 pathway of human progress unheeded by the passing throngs. 

 Lamarck as.sumed first, what is universally granted ; namely, 

 the influence of use and disuse of organs upon individual de- 

 velopment, and second, what is generally denied; namely, 

 the perpetuation of such influence by heredity. Thus let us 

 suppose a grouj) of early race horses to have increased their 

 speed by training until they were materially faster than their 

 parents. If now such increase in speed were handed down 

 to their offspring, and these in turn improved by further 

 training, aiul so on from generation to generation, there 

 would evolve in time the speedy animal of today. Or if, on 

 the other hand, a race of fishes living at one time in the open, 

 for some reason or other, perhaps to escape the attack of ene- 

 mies, took to dwelling in caves, where sight was of little ad- 

 vantage; there would in course of time, through lack of use 

 of sight, develop the blind cave fishes of the present. The 

 theory is the prettiest and simplest of the modua operandi of 

 evolution which has been proposed, and could it be proven, 

 would remove many difficulties in our path. Unfortunately 

 however proof thus far is lacking. Skepticism toward the 

 theory has been mainly founded on failure of mutilations of 

 various sorts (circumcision among the Jews, cramping of 

 feet by the Chinese, docking of horses' tails), and finally Weis- 

 mann's classical experiments in amputating the tails of twen- 

 ty-two geiu'rations of mice, to produce any inheritable modi- 

 fication whatever in the parts so mutilated. It should be 

 noted however that while Lamarck's theory postulates use 

 and disuse as the prime factors in causing change, some of 

 the mutilations above cited do not involve the factors of use 



■* Ultiniatoly "internal" chantros tlu'iiisc'l\es are prol)aT)ly roforalile to 

 external causes. I have in niiml tlie manifold metabolic changes, which 

 may produce variation. Regarding this we have no certain knowledge. 



