THE VALUE OF EXTERNAL SUPPORT 33 



is not necessary to be a biologist in order to 

 comprehend the details and the bearings of this 

 theory. At the outset, when naturalists them- 

 selves were often hopelessly puzzled, the theory 

 was clearly understood by able thinkers who were 

 not students of biology, or indeed in some cases 

 of any of the sciences. And at the present time 

 such support is of the highest importance when, 

 within the boundaries of the sciences most nearly 

 concerned, the intense and natural desire to try 

 all things is not always accompanied by the 

 steadfast purpose to hold fast that which is good. 



LAMARCK'S HYPOTHESIS AND THE HEREDITARY 

 TRANSMISSION OF ACQUIRED CHARACTERS 



The greatest change in evolutionary thought, 

 since the publication of the Origin, was wrought, 

 after Darwin's death, by the appearance of that 

 wonderful and beautiful theory of heredity which 

 looks on parents as the elder brother and sister of 

 their children. In this theory, itself an outcome 

 of minute and exact observation (see p. 39), 

 Weismann raised the question of the hereditary 

 transmission of acquired characters, the very 

 foundation of Lamarckian and Spencerian evolu- 

 tion. Darwin accepted this transmission, and it 

 was in order to account for 'such facts as the 

 inherited effects of use and disuse, &c.,'^ that 

 he thought out his marvellous hypothesis of 



> See the letter to Huxley, July 12 (1865 ?), in Life and Letters, 

 iii. 44. 



D 



