366 Appendix B 



assume that the one produces the other, while of course the 

 Weismannians must deny such a conclusion. 



"If it were not necessary to assume that a congenital varia- 

 tion appropriate to the habit should follow immediately when the 

 habit changes, this difficulty would be greatly lessened. It may 

 be admitted that it is so improbable as to be inconceivable that 

 a new habit should be followed immediately by a congenital 

 change in structure appropriate to the new habit, unless there 

 be some inheritance of acquired variation. But it is quite 

 probable, even upon the principle of haphazard variations in 

 all directions, that some such congenital variation might appear 

 in course of time. If the individuals could be kept in their 

 new habit long enough, it would be pretty sure that eventually 

 some congenital variation would appear of an appropriate 

 character. Now the acquired characters will serve to preserve 

 the individual in the new conditions. When an animal adopts 

 a new habit its body begins to change at once, and he soon 

 acquires a development of his muscles and bones adapted to 

 his new habit. He may, indeed, not transmit these characters, 

 and his offspring may be at birth no better off than he was at 

 birth. Each generation acquires these characters for itself so 

 long as the conditions remain the same. But the new charac- 

 ters, even though not congenital, adapt the individual to its 

 new conditions and enable him to live successfully in these 

 conditions. These individuals are therefore able to contend 

 successfully in the struggle for existence, their acquired charac- 

 ters being just as useful to them as they would have been if 

 congenital. This is repeated, generation after generation, similar 

 acquired characters being redeveloped by each generation. 



" Remembering then the great numbers of variations that are 

 constantly occurring as the result of modifications of the germ 

 plasm, it is probable, indeed certain, that after a time some 

 congenital variation will appear which will be of direct use to 

 the animals in their new habits. During all this time the 

 majority of variations will appear and as quickly disappear, 

 since, being of no special use, there will be nothing to preserve 

 them, and cross-breeding will soon eliminate them. But when, 



