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J UNIVERSITY 



CHAPTER I 



PRINCIPLES OF BREEDING 



Family Resemblance Heredity Darwin's Theory of Pangenesis Weis- 

 mann's Continuity of Germ-plasm Theory Archdall Reid on Re- 

 capitulation a Leading Factor in Heredity Force of Inheritance 

 Ewart's Telegony Experiments Constitutional Weakness Imagi- 

 nation Crossing and In-and-in Breeding, including Line-breeding 

 Natural Breeding Formation of New Breeds Atavism in Pure 

 Breeds and in Crosses Domestication Barrenness Latent 

 Characters Mendel's Laws of Inheritance. 



THE strong family resemblance which is seen both in 

 the human species and amongst animals related to 

 each other is a direct consequence of the existence of the 

 first law of breeding, viz., that " like begets like," " or tends to 

 produce like." Other laws are in operation at the same time ; 

 consequently, when an organism comes within the immediate 

 spheres of their action, the effects of this and various other laws 

 are modified to harmonise with surrounding conditions. The 

 influence of a parent, as such, in his or her procreative 

 function, is not always exerted under exactly the same 

 conditions ; and we have differences among individuals, 

 alike in many respects, which distinguish them from one 

 another. To the uneducated eye, every member of a herd of 

 polled cattle or of a flock of Southdown ewes looks exactly 

 like its neighbour, and a townsman marvels when he is told 

 that some shepherds know individually every member of a 

 flock of several hundreds. Moreover, both wild and domesti- 

 cated animals recognise each other by eyesight as well as by 

 smell. The existence of exceptions to this law of similarity 

 is the great incentive to the stock breeder to try his skill in 

 producing or discovering and then conserving superior 

 qualities in his animals. Effort in this direction is as 

 ancient as the civilisation of Egypt, and the Arab horse is 

 a striking example of its success. 



