LrV^ STOCK. 



165 



ture, and either went down und«r nar 

 tui^ selection, or became good species 

 before they came into our hands. 

 However, modified strains may yet be 

 hybridized, and sterile hybrids may 

 often be propagated asexually. 



The classic hybrid is the mule or 

 hinny, the cross between the horse 

 and the ass, aud is nearly always ster- 

 ile. The lion and the tiger mate free- 

 ly, in captivity at least, but the mat- 

 ing is in most cases fruitless. Even 

 here, however, hybrids have been 

 bom. 



The Reciprocal Cross. 

 Strange as it may at first appear, 

 the two possible crosses by inter- 

 change of the sexes often, though not 

 always, differ substantially. It is said 

 that the common mule more nearly 

 resembles the ass, and the hinny the 

 horse. Other instances have been 

 noted, and the point has been urged 

 that reciprocal crosses are in general 

 dissimilar. It is the writer's opinion 

 that the rule applies only to those par- 

 ticular characters in which the one 

 parent (either male or female) is pre- 

 potent over the other because of sex. 

 However, statistical evidence on re- 

 ciprocal crosses is almost totally lack- 

 in;?. 



The whole subject of hyT)ridization 

 seems at present to promise little of 

 interest to animal breeders beyond 

 the production of the common mule, 

 but if we may place a shrewd guess, 

 it will yet be found a fruitful source of 

 new varieties in certain races of 

 plants,-, in which propagation is so 

 easily effected by budding, grafting, 

 or other form of a sexual multiplica- 

 tion, thus avoiding the effects of Men- 

 del's law in a way quite impossible 

 with animals. 



Line Breeding 

 By 'line breeding" is meant the re- 

 striction of selection and mating to 

 the individuals of a single line of de- 

 scent. The purpose of this system of 

 breeding is real breed improvement, — 

 to get the best that can be gotten oust 

 of the race and better than ever be- 

 fore if iMJSsrble. 



"Line breeding excludes everything 

 outside the approved and chosen line of 

 breeding. It n6t only combines ani 

 mals very similar in their characters, 

 but it narrows the pedigree to few 

 and closely related Idnes of descent. 

 This "purifies" the pedigree rapidly 



and gives the ancestry the largest pos- 

 sible opportunity. T5ie system is emin- 

 ently conservative. It discourages 

 variability, and rapidly reduces it to 

 a minimum. Moreover, whatever 

 variations do occur will be in line 

 with the prominent characters of the 

 chosen branch of the breed. 



Advantages of Line Breeding. 

 The nature of results secured by this 

 system can almost certainly be pre- 

 dicted; and when they do appear, and 

 improvement is at hand, it is backed 

 up by the most powerfiil hereditary 

 influence obtainable, because of the 

 simplicity and strength of the ances- 

 try, which, if the selection has been 

 good, all "pulls" In the same direction. 

 The records of all breeds will show 

 the pronounced results that have fol- 

 lowed judicious line breeding. A 

 volume could be filled with pictures 

 of famous animals so producer 

 Those shown are the swine, for the 

 reason that the pig Is popularly suxh 

 posed to be the most sensitive to closs 

 breeding. 



Disadvantages of Line Breeding. 



The chief danger in line breeding 

 is that the breeder will select by 

 pedigree, abandoning real individual 

 selection. A line-bred pedigree Is 

 valuable or dangerous In exact pro- 

 portion as the individuals have been 

 kept up to grade. It will not replace 

 selection, but, on the contrary, calls 

 for the most discriminating care wltn- 

 In the line. 



If the oreeder selects by paper, and 

 not In the yards, and a few genera- 

 tions of inferior animals creep In, then 

 line breeding will consign the whole 

 bunch to the limbos quicker and more 

 certainly than will any other known 

 system of breeding, — a fate that has 

 overtaken more than one line that un- 

 fortunately became prematurely fa^i- 

 ionable. 



L'ne Breeding the Best System for 

 Improvement. 



No other system of breeding has 

 ever secured the results that line 

 breeding has secured, and if the pre- 

 sent state ot knowledge is reasonably 

 sound, no other system will ever be so 

 powerful in getting the most possible 

 out of a given breed or variety, es- 

 pecially of animals, and this with the 

 greatest certainty as we go along. 

 The only requirement Is, not to aban- 



