6 14 PRACTICAL PROBLEMS 



of the dam. This form of breeding is practiced when it is de- 

 sired to secure all that is possible of the blood of the sire. 



2. Breeding the dam to her own son or sons successively, 

 thus increasing the blood lines of the female side. This form is 

 practiced when it is the dam's blood lines that are to be 

 preserved and condensed. Both systems are necessarily limited 

 to the lifetime of the individuals involved. Either system can 

 of course be approximated by the use of granddaughter or 

 grandson, which would by common consent be called inbreed- 

 ing, but relationship more remote would generally be regarded 

 merely as line breeding. 



3. Breeding together of brother and sister, a form of in- 

 breeding which preserves the blood lines from both sire and dam 

 in equal proportions. It is inferior to either of the others as a 

 means of strengthening previously existing blood lines, but it is 

 freely employed when the combination has proved exceptionally 

 successful, virtually establishing a new type. It has all the dangers 

 of the other two, and in a larger degree, because we have prac- 

 tically no acquaintance with the new combination, whereas in 

 strengthening the proportion of one line of ancestry over another, 

 whether it be that of the sire or that of the dam, we are dealing 

 with previously existing blood lines known to be harmonious. 



Among plants there are two forms of inbreeding, namely : 



1. That in which the fertilization is with pollen from another 

 flower on the same plant. 



2. That in which fertilization is by pollen of the same flower. 

 This, being hermaphroditic, is the closest imaginable inbreeding, 

 and exceeds anything that is possible with animals. 



Advantages of inbreeding. Nobody claims advantages in in- 

 breeding per se, but it is the acme of line breeding, and when 

 superior individuals are at hand it is the most powerful method 

 known of making the most of their excellence. It is the method 

 by which the highest possible percentage of the blood of an 

 exceptional individual or of a particularly fortunate " nick " ran 

 be preserved, fused into and ultimately made to characterize an 

 entire line of descent on both sides. 



If persisted in, the outside blood disappears by the same law 

 that governs grading, and the pedigree is speedily enriched to 



