616 PRACTICAL PROBLEMS 



Plenty of examples of successes can be instanced, and every 

 breeder is familiar with them. The failures have been many, 

 but they are not to be counted here, for the blood lines in- 

 volved are long since extinct. 



Special dangers from inbreeding. Tradition everywhere has it 

 that inbreeding, if long continued, is practically certain to end 

 in loss of vigor and of fertility, and plenty of instances are given 

 to "prove" it. 



Now a rational consideration of the principles of transmission 

 has already led us to expect that bad characters as well as good 

 will be intensified. We could not expect so powerful a method 

 to work only to our advantage and to grant immunity from dis- 

 advantage in all cases. 



What we want to know is whether, in respect to trouble, 

 we are to look out for likelihood or for certainty ; whether disas- 

 ter is inevitable, or only extremely probable. This question has 

 been much befogged by certain catchy statements such as, 

 " Nature abhors incestuous breeding," all of which confuse an 

 ethical and social question with the biological one in which only 

 we are interested. 



Inbreeding not necessarily disastrous. Our attention is con- 

 stantly called to " nature's provisions for preventing inbreeding," 

 and to " ingenious devices for inducing cross pollination by 

 insect aid " ; but we are not reminded that many species of 

 plants are self -pollinated, nor is our attention called to the many 

 famous sires that were strongly inbred, nor to the fact that in 

 nature among gregarious animals the head of the herd is sire of 

 practically all the young (so long as he remains master), many of 

 of whom are thus doubly his. Nor do we have it called to our 

 attention that, while corn seems peculiarly sensitive to inbreed- 

 ing, wheat is self-fertilizing to the closest possible degree, and 

 that it is perhaps the most vigorous, prolific, and all-round cos- 

 mopolitan success among our domestic plants. 



Lack of vigor and low fertility the two most common defects. 

 If what has been said and shown has any meaning, it is that any 

 character can be bred up or down, strengthened or weakened 

 by this method of breeding. Why then its evil reputation with 

 respect to vigor and fertility ? Is there some inherent injury 



