28 THE GROWTH OF GROUPS 



repulsive to mankind. Darwin, who gave the matter much 

 attention and was inclined to believe in a law against 

 inbreeding, considered that the available evidence " plainly 

 shows that good follows from crossing, and less plainly 

 that evil follows from close interbreeding." In these 

 words there are two separate statements of opinion. 

 From the context we see that the first statement is 

 partially the outcome of the general experience that 

 mongrel stock are large and vigorous, but chiefly the 

 result of Darwin's own experiments, which proved that 

 hermaphrodite plants produce more seed when they are 

 the offspring of a crossed union than otherwise. It is 

 evident however that Darwin's experiments were directed 

 to show that the various cross-fertilizing mechanisms of 

 plants were of utility, he did not consider it impossible 

 for a single plant, which happened to set seed, to stock 

 a large area with its descendants. This is plainly shown 

 in the following words, which are his : " When a single 

 plant of a new species is introduced into any country, if 

 propagated by seed, many individuals will be raised, so 

 that if the proper insects be present there will be crossing." 

 Now, as to the second statement of opinion which is 

 contained in the second half of the first passage quoted : 

 it is important for my argument to emphasize the fact 

 that Darwin, after giving the matter much attention, 

 thought that the evidence for evil following close in- 

 breeding was not conclusive. It must therefore be 

 admitted that it is uncertain whether inbreeding is 

 harmful in all cases. On the other hand, there is evidence 

 to prove that inbreeding has not been deterimental in 

 certain cases. Rabbits, pigs, and goats, a few at a time, 

 have been introduced into islands on many occasions and 



