HEREDITY 133 



ness in the use of terms. The literature of animal-breed- 

 ing is still less exact in its terminology. It seems impor- 

 tant, therefore, that in the very beginning we should have 

 as clear a conception as possible of the definitions of 

 heredity which have been proposed. Heredity is the 

 organic relation existing between an individual and its 

 ancestors. It is the continuous biological thread connect- 

 ing generations of organic beings. Heredity is " organic 

 resemblance based on descent. " 1 Thomson 2 has defined 

 heredity as " the organic or genetic relation between 

 successive generations." " Understood in its entirety," 

 says Herbert Spencer, 3 " the law is that each plant or 

 animal, if it reproduces, gives origin to others like itself ; 

 the likeness consisting, not so much in the repetition of 

 individual traits as in the assumption of the same general 

 structure." " The transference of similar characters 

 from one generation of organisms to another, a process 

 effected by means of the germ-cells or gametes." 4 " By 

 inheritance," says Lock, 5 " we mean those methods and 

 processes by which the constitution and characteristics 

 of an animal or plant are handed on to its offspring, this 

 transmission of characters being, of course, associated 

 with the fact that the offspring is developed by the pro- 

 cesses of growth out of a small fragment detached from 

 the parent organism." Another definition of heredity 

 is that it is the tendency of the offspring to be like the 

 parents. There exists a definite organic resemblance or 



1 Castle, " Heredity in Relation to Evolution and Animal 

 Breeding." 



2 Thomson, "Heredity" (1908), p. 13. 



3 Herbert Spencer, " Principles of Biology," vol. I, p. 301. 



' 4 R. H. Lock, " Recent Progress in the Study of Variation, 

 Heredity and Evolution," 1906, p. 292. 



5 Loc. cit., p. 1. 



