bandrv including Poultry Husbandry, Cereal Husbandry 

 or Agronomy, and Horticulture where direct applications 

 are made to the better breeding of animals and plants. 



Heredity has been defined as "the organic or genetic 

 relation between successive generations," and again as 

 "the germinal resemblance among organisms related by 

 descent." Genetics is "the science which deals with the 

 coming into being of organisms" by breeding carried on 

 from generation to generation. Essentially Genetics has 

 to do with the study of heredity, and its main object is to 

 determine not only the mode of action of the germinal fac- 

 tors concerned in bringing about the relation implied in 

 heredity, but. also that of the external agencies that may 

 affect the development of the new individual. 



Genetics is breeding under rigid control so that we 

 may know what is happening. At the present time the 

 control is such that it is not possible to know all that is 

 happening, but as Genetics is one of the youngest sciences, 

 dating as it does from 1900 when Mendel's discoveries 

 were made known, we may confidently look forward to a 

 time when a method of continuous control may be employ- 

 ed in all breeding experiments. 



We can probably all agree with Bateson when he says: 

 "An exact determination of the laws of heredity will prob- 

 ably work more change in man's outlook on the world and 

 in his power over nature than any other advance in natural' 

 knowledge that can be clearly foreseen." 



Chapter 1— THE WORLD OF LIVING THINGS 



It is very probable that ever since man's appearance 

 on the earth the living things about him were more or less 

 closely observed and their most evident likenesses and 

 differences noted. In other words, our early ancestors 

 made rough groupings of the animals and plants with 

 which they came into contact. One of the first observers 

 to record his observations was Aristotle ( t(g #. %m B.C.). 

 His groupings were crude according to present-day stan- 

 dards as they were based mainly on external similarities 

 of structure, but they remained practically unaltered for 

 over 2,000 years, until the time of Ray (1628-1705) and 

 Linnaeus (1707-1778). Ray defined the term species but 

 it was reserved for Linnaeus to establish the binomial system 

 of nomenclature and the grades of classification, viz.. Class, 

 Order, Genus, Species and Variety in his great work "Sys- 

 tema Naturae." 



