SEVENTH ANNUAL YEAR BOOK— PART VI. 251 



ness, openly declare at meetings of this kind that they did not care to 

 hear it discussed. While we all have the deepest respect for our fellow- 

 men who have made a success of their life's tasks, and while I would be 

 the last person to unjustly criticize another for his opinion, it would not 

 be out of place to remind those who take such radical views with refer- 

 ence to new ideas that in spite of all success they may have attained, it 

 is still possible that they may not know all about the laws of breeding. 

 We should not be led astray by new theories; we should not accept facts 

 of vital importance to our business and our personal welfare without 

 thorough investigation, but on the other hand we should never close our 

 ears or our eyes to things that are going on about us. 



With these introductory remarks, let us inquire as to the nature of 

 Mendel's law. What does it teach? In brief, it teaches that there is a 

 principle underlying sexual reproduction in the organic world by means 

 of which the breeder can with a degree of certainty foretell results at 

 least to an extent never known before in its discovery. It includes at 

 least three important principles: First, the principle of dominance; sec- 

 ond, the purity of germ cells; and third, the principle or law of proba- 

 bility, which explains what we may expect from certain lines of breeding. 

 All these factors must be fully understood before the law as a whole can 

 be comprehended. With regard to the principle of dominance the law 

 teaches that the different characteristics or characters of individuals, or 

 of breeds, such as polled heads in certain cattle, special color markings, 

 feeding qualities, early maturity, milk giving qualities, etc., are present 

 as entities in the original germ cells from which all organic individuals 

 spring; that these characters have different degrees of intensity, or in 

 other words, that their powers of reproducing themselves vary. 



In the past we have designated the power of an individual to impress 

 its characters upon its offspring by the term "prepotency," which term, 

 however, has stood for something that no one could clearly explain. 

 Mendel's law explains prepotency so that it becomes intelligible to any- 

 body. It has been called the law of dominance, and it teaches that when 

 two animals of the same or of different breeds, with characters of differ- 

 ent degrees of potentiality, are crossed, only one character of each char- 

 acter pair (the corresponding characters of male and female) asserts 

 itself. The character that asserts itself is said to be dominant and the 

 other recessive. In the first cross of two plants or of two animals, both 

 the dominant and recessive characters are found side by side in the same 

 germ cell of the hybrid or the offspring; but, as will be seen later, upon 

 reaching maturity, this character pair separates, breaks up and the 

 breeder may retain either the dominant or the recessive character, in 

 accordance with his own wishes. In other words, the law assumes the 

 purity of germ cells, which is its great underlying principle. 



The significance of the purity of germ cells is this: Any hybrid, 

 whatever its nature, produces mature germ cells which contain only one 

 of the characters of its parents. In case the characters under considera- 

 tion of the male and the female are of equal potency, which in practice 

 would practically never be the case, the offspring would sometimes resem- 

 ble one and sometimes the other parent, so far as the character pair 

 under consideration is concerned. If, on the other hand, the character of 



