372 THE HISTORY AND SCOPE OF ZOOLOGY IX 



Lamarck argued, a structural alteration amounting to 

 such difference as we call " specific " might be thus 

 acquired. The familiar illustration of Lamarck's 

 hypothesis is that of the giraffe, whose long neck 

 might, he suggested, have been acquired by the efforts 

 of a primitively short-necked race of herbivores, who 

 stretched their necks to reach the foliage of trees in 

 a land where grass was deficient, the effort producing 

 a distinct elongation in the neck of each generation, 

 which was then transmitted to the next. This process 

 is known as "direct adaptation"; and there is no 

 doubt that such structural adaptations are acquired 

 by an animal in the course of its life. Whether such 

 acquired characters can be transmitted to the next 

 generation is a separate cjuestion. It was not proved 

 by Lamarck that they can be, and, indeed, never has 

 been proved by actual observation. Nevertheless it 

 has been assumed, and also indirectly argued, that 

 such acquired characters must be transmitted. Dar- 

 win's o;reat merit was that he excluded from his 

 theory of development any necessciTy assumption of 

 the transmission of acquired characters. He pointed 

 to the admitted fact of congenital variation, and he 

 showed that these variations to all intents and pur- 

 poses have nothing to do with any characters acquired 

 by the parents, but are arbitrary and, so to speak, 

 non-significant. Their causes are extremely difficult 

 to trace in detail, but it appears that they are largely 

 due to a " shaking up " of the living matter which 

 constitutes the fertilised germ or embryo-cell, by the 

 process of mixture in it of the substance of two cells, — 



